[doc] fix smalldet doc and readme (PaddlePaddle#7775)

* fix smalldet docs, test=document_fix

* fix smalldet configs and readme, test=document_fix

Author: nemonameless

configs/pphuman/README.md

@@ -13,7 +13,7 @@ PaddleDetection团队提供了针对行人的基于PP-YOLOE的检测模型，用
 |PP-YOLOE-l|   CrowdHuman   |  48.0  |  81.9  | [下载链接](https://paddledet.bj.bcebos.com/models/ppyoloe_crn_l_36e_crowdhuman.pdparams) | [配置文件](./ppyoloe_crn_l_36e_crowdhuman.yml) |
 |PP-YOLOE-s|   业务数据集   |  53.2  |  -  | [下载链接](https://paddledet.bj.bcebos.com/models/ppyoloe_crn_s_36e_pphuman.pdparams) | [配置文件](./ppyoloe_crn_s_36e_pphuman.yml) |
 |PP-YOLOE-l|   业务数据集   |  57.8  |  -  | [下载链接](https://paddledet.bj.bcebos.com/models/ppyoloe_crn_l_36e_pphuman.pdparams) | [配置文件](./ppyoloe_crn_l_36e_pphuman.yml) |
-|PP-YOLOE+_t-aux(320)|   业务数据集   |  45.7  |  81.2  | [下载链接](https://paddledet.bj.bcebos.com/models/pyoloe_plus_crn_t_auxhead_320_60e_pphuman.pdparams) | [配置文件](./ppyoloe_plus_crn_t_auxhead_320_60e_pphuman.yml) |
+|PP-YOLOE+_t-aux(320)|   业务数据集   |  45.7  |  81.2  | [下载链接](https://paddledet.bj.bcebos.com/models/ppyoloe_plus_crn_t_auxhead_320_60e_pphuman.pdparams) | [配置文件](./ppyoloe_plus_crn_t_auxhead_320_60e_pphuman.yml) |
 
 
 **注意:**

configs/ppvehicle/README.md

@@ -20,7 +20,7 @@ PaddleDetection团队提供了针对自动驾驶场景的基于PP-YOLOE的检测
 |PP-YOLOE-s|   PPVehicle9cls |   9    |  35.3 | [下载链接](https://paddledet.bj.bcebos.com/models/mot_ppyoloe_s_36e_ppvehicle9cls.pdparams) | [配置文件](./mot_ppyoloe_s_36e_ppvehicle9cls.yml) |
 |PP-YOLOE-l|   PPVehicle     |   1    |  63.9 | [下载链接](https://paddledet.bj.bcebos.com/models/mot_ppyoloe_l_36e_ppvehicle.pdparams) | [配置文件](./mot_ppyoloe_l_36e_ppvehicle.yml) |
 |PP-YOLOE-s|   PPVehicle     |   1    |  61.3  | [下载链接](https://paddledet.bj.bcebos.com/models/mot_ppyoloe_s_36e_ppvehicle.pdparams) | [配置文件](./mot_ppyoloe_s_36e_ppvehicle.yml) |
-|PP-YOLOE+_t-aux(320)|   PPVehicle   |   1    |  53.5  | [下载链接](https://paddledet.bj.bcebos.com/models/pipeline/ppyoloe_plus_crn_t_auxhead_320_60e_ppvehicle.pdparams) | [配置文件](./ppyoloe_plus_crn_t_auxhead_320_60e_ppvehicle.yml) |
+|PP-YOLOE+_t-aux(320)|   PPVehicle   |   1    |  53.5  | [下载链接](https://paddledet.bj.bcebos.com/models/ppyoloe_plus_crn_t_auxhead_320_60e_ppvehicle.pdparams) | [配置文件](./ppyoloe_plus_crn_t_auxhead_320_60e_ppvehicle.yml) |
 
 
 **注意:**

configs/smalldet/DataDownload.md

@@ -0,0 +1,99 @@
+# 小目标数据集下载汇总
+
+## 目录
+- [数据集准备](#数据集准备)
+    - [VisDrone-DET](#VisDrone-DET)
+    - [DOTA水平框](#DOTA水平框)
+    - [Xview](#Xview)
+    - [用户自定义数据集](#用户自定义数据集)
+
+## 数据集准备
+
+### VisDrone-DET
+
+VisDrone-DET是一个无人机航拍场景的小目标数据集，整理后的COCO格式VisDrone-DET数据集[下载链接](https://bj.bcebos.com/v1/paddledet/data/smalldet/visdrone.zip)，切图后的COCO格式数据集[下载链接](https://bj.bcebos.com/v1/paddledet/data/smalldet/visdrone_sliced.zip)，检测其中的**10类**，包括 `pedestrian(1), people(2), bicycle(3), car(4), van(5), truck(6), tricycle(7), awning-tricycle(8), bus(9), motor(10)`，原始数据集[下载链接](https://github.com/VisDrone/VisDrone-Dataset)。
+具体使用和下载请参考[visdrone](../visdrone)。
+
+### DOTA水平框
+
+DOTA是一个大型的遥感影像公开数据集，这里使用**DOTA-v1.0**水平框数据集，切图后整理的COCO格式的DOTA水平框数据集[下载链接](https://bj.bcebos.com/v1/paddledet/data/smalldet/dota_sliced.zip)，检测其中的**15类**，
+包括 `plane(0), baseball-diamond(1), bridge(2), ground-track-field(3), small-vehicle(4), large-vehicle(5), ship(6), tennis-court(7),basketball-court(8), storage-tank(9), soccer-ball-field(10), roundabout(11), harbor(12), swimming-pool(13), helicopter(14)`，
+图片及原始数据集[下载链接](https://captain-whu.github.io/DOAI2019/dataset.html)。
+
+### Xview
+
+Xview是一个大型的航拍遥感检测数据集，目标极小极多，切图后整理的COCO格式数据集[下载链接](https://bj.bcebos.com/v1/paddledet/data/smalldet/xview_sliced.zip)，检测其中的**60类**，
+具体类别为：
+
+<details>
+
+`Fixed-wing Aircraft(0),
+Small Aircraft(1),
+Cargo Plane(2),
+Helicopter(3),
+Passenger Vehicle(4),
+Small Car(5),
+Bus(6),
+Pickup Truck(7),
+Utility Truck(8),
+Truck(9),
+Cargo Truck(10),
+Truck w/Box(11),
+Truck Tractor(12),
+Trailer(13),
+Truck w/Flatbed(14),
+Truck w/Liquid(15),
+Crane Truck(16),
+Railway Vehicle(17),
+Passenger Car(18),
+Cargo Car(19),
+Flat Car(20),
+Tank car(21),
+Locomotive(22),
+Maritime Vessel(23),
+Motorboat(24),
+Sailboat(25),
+Tugboat(26),
+Barge(27),
+Fishing Vessel(28),
+Ferry(29),
+Yacht(30),
+Container Ship(31),
+Oil Tanker(32),
+Engineering Vehicle(33),
+Tower crane(34),
+Container Crane(35),
+Reach Stacker(36),
+Straddle Carrier(37),
+Mobile Crane(38),
+Dump Truck(39),
+Haul Truck(40),
+Scraper/Tractor(41),
+Front loader/Bulldozer(42),
+Excavator(43),
+Cement Mixer(44),
+Ground Grader(45),
+Hut/Tent(46),
+Shed(47),
+Building(48),
+Aircraft Hangar(49),
+Damaged Building(50),
+Facility(51),
+Construction Site(52),
+Vehicle Lot(53),
+Helipad(54),
+Storage Tank(55),
+Shipping container lot(56),
+Shipping Container(57),
+Pylon(58),
+Tower(59)
+`
+
+</details>
+
+，原始数据集[下载链接](https://challenge.xviewdataset.org/)。
+
+
+### 用户自定义数据集
+
+用户自定义数据集准备请参考[DET数据集标注工具](../../docs/tutorials/data/DetAnnoTools.md)和[DET数据集准备教程](../../docs/tutorials/data/PrepareDetDataSet.md)去准备。