fixed CMSfields js and css issues
Now uses GridFieldExtensions for the sortable rows
Implement getFilename and getName to stick comparely to File API.
FIX: Resolve issue of not being able to attach documents on draft pages
Make DMSDocument methods chainable. PHPDoc cleanup.

- Remove unimplemented getAllTags()
- Add .DS_Store as ignored file
- Add gridfieldextensions as a declared dependancy.