Merge pull request #1730 from blackpuppy/zh

[zh] fix language errors and correct some errors in original text
Update form.rst

There was a syntax error in the documentation
Merge pull request #1738 from azerto00/patch-1

Update form.rst
[fr] update french translation
Uppercase 'Engine' Should be Lowercase

Uppercase 'Engine' in the custom session handler example breaks the example.
Merge pull request #1744 from jadedcore/master

Uppercase 'Engine' Should be Lowercase
[zh_CN] rename zh to zh_CN for Simplified Chinese, leaving zh_TW for Traditional Chinese (ref: http://sphinx-doc.org/config.html#confval-language)
[zh] fix sphinx build warning