Admin AGL list for media

[Floby]

some notable added features

• one click selection when selecting from popup (tinymce)
• indicate how many times the media is referenced by other contents
• group media by sha1
  • disable editing, deleting and whatnot for grouped media
  • display link to another admin page listing only media with this sha1
  • offer button back from that list to the main media list

there are some TODOs left

• move some use detection back to Centurion_DbTable[Row_]Abstract because it is generic enough to be widely used.
• admin list looks dead ugly when dealing with anything else than images
• generic form elements allowing to pick directly from the mediacenter (not just from rte fields)

[Floby]

@lchenay Removed trace of getCdnUrl and view var displayDuplicate is always boolean

[lchenay]

Can't be merge. I have a test failed:

• Centurion_Form_ModelTest::testSaveManyToMany()

2 unknown variables in Centurion_Form_Model_Abstract:822

• $refLocalArray
• $refForeignArray

See my branch merge/floby/feature-mediacenter

[Floby]

I merged with your merge/floby/feature-mediacenter and reverted the faulty commit. apparently the Form_Model_Abstract doesn't use references on interesection tables for many to many relationships.