Sortedcontainerupdates (#787)

* Major update to sorted containers.

    Address issue 239: Dict constructors on typed data but without explicit type declarations
    should no longer return {Any,Any} items because collect is now used when explicit types
    are omitted

    Address issue 479: Deprecate insert!, pop!(s), introduce popfirst!, poplast!,
       ss_push!, sd_push!, smd_push!

    Address issue 528: push! documentation improved

    Address issue 667: Docs extensively cleaned up and much greater use of
      documenter.jl

    Address issue 669: Expanded use of tokens including a:b notation for tokens

    Address issue 671: Add reverse iteration

    Address issue 742: New union, merge, symdiff, setdiff, intersect algorithms for
    sorted containers to improve performance

    Address issue 726: Clarify docs on insert! (now deprecated)

    Address issue 767: Implement firstindex, lastindex, reverse for sorted container iteration

    Address issue 781: Use collect on an intermediate step
    to infer types in untyped construction of sorted containers

    Also, this commit cleans up the constructors and
    adds two new iteration-helper functions inclusive_key
    and exclusive_key that were useful in my own work.

  Documented the fact that values(s) is not currently writeable.

  Updated testset with comments to refer to issues that have been resolved

Author: StephenVavasis

docs/Project.toml

@@ -1,4 +1,6 @@
 [deps]
+Coverage = "a2441757-f6aa-5fb2-8edb-039e3f45d037"
+DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 
 [compat]