string: Convert string module to package and import templatelib.

Convert the existing `string` module into a package with `__init__.py`
and `templatelib.py`.  This is needed to support t-strings (if they are
enabled) because there is a built-in `string.templatelib` module with
built-in `Template` and `Interpolation` classes.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

python-stdlib/string/manifest.py

@@ -1,3 +1,3 @@
-metadata(version="0.1.1")
+metadata(version="0.2.0")
 
-module("string.py")
+package("string")

python-stdlib/string/string.py python-stdlib/string/string/__init__.pypython-stdlib/string/string.py renamed to python-stdlib/string/string/__init__.py

@@ -0,0 +1,5 @@
+# Import built-in t-string classes if they exist.
+try:
+    from ustring.templatelib import *
+except:
+    pass