fix greater/smaller filters for pymongo

filter never worked, because value is passed as string and mongodb returns zero documents
Made InlineFieldList compatible with WTForms 2
WTForms 2 compatibility

Replaced deprecated TextField with StringField
No meta needed for template creation
Merge pull request #676 from arsgeografica/wtf2

WTForms 2 compatibility
Fix incorrect usage of NotImplemented

`NotImplemented` is a constant singleton used in rich comparison
overloading. It is not callable, and is not an exception.
`NotImplementedError` is a built in exception.
Merge pull request #685 from ajalt/master

Fix incorrect usage of NotImplemented constant
Merge pull request #660 from Raz0r/patch-6

fix greater/smaller filters for pymongo
Fix compatible problem for InlineModelFormList with two primary keys

the type of primary of model with two or more primary keys is tuple, which is different from that of models with one primary.
InlineModelFormField and InlineModelFormList can only work with str type primary key.