Beginning media cleanup with media sources

Media sources deal with storage, removal and URLs
Now using media source for storing uploaded files
Media info usage

Now no need for the generic "media service"
Very kludgy cropping
No more generic media service
URL double slash fix for media sources
Child display of media
Inserting of rendered media templates

Also tweaked the CodeMirror insert (used by GoogleDrive) to insert at
the cursor position rather than at the end of the current text.
Database level cascade actions for media and crops
Quick URL cleanup