Czech language support

Czech language support.

Fixed typo in fileadmin.py

A bug occurred in get_one, solved in this change.

Cast to ObjectId is not needed in pymongo backend

Add Simplified Chinese and Traditional Chinese translations

Fixing jinja2 error in admin/lib.html

UndefinedError: the inline if-expression on line 79 in 'admin/lib.html' evaluated to false and no else section was defined.

Fixed issue where some required fields would not be properly validated at the form level

- Using newer wtf.validators.DataRequired, old one is going to be deprecated

HTML fix: use javascript:void(0) instead of # so page doesn't jump

added persian language

make bulk deletes go through `delete_model`

I'm not sure this is ideal (might hide some errors?) but it's the easiest way
to use the hook for both kinds of delete.

Proposition for translation : updating french translation