Fixes #287

By skipping the save logic when both the new value and the old value are blank, we stop wasting time doing the persistence logic for a change which does nothing and we also avoid triggering the bug where images sometimes get unset.
Change name of JS object, fixed #290
Removing unnecessary isset checks as discussed.
Merge pull request #288 from darkliquid/master

Fixes #287
Revamped Advanced File Upload fields

The `file_advanced` and `image_advanced` fields now use the
`underscore.js` library to create new items on the client side.
Misc tweaking with color and taxonomy
oEmbed Tweaking
Field creation logic now in a seperate function.

Prep work for field groups
Fixing bugs
show_fields fixes
Merge pull request #292 from funkedgeek/master

File and Image advanced now use Underscore.js