Intelligent Media Defaults

(this stems from a #drupal-dojo discussion)

Right now, there are a lot of steps involved in getting Media set up for new content types, etc. Typically it will be best to have Media enabled everywhere except possibly a few places, because Media adds on to existing fields without disrupting normal functionality in most cases.

Add a new "Defaults" configuration tab to the Media module, where you can configure for typical behavior. On install, the state should be enabled for all fields (with applicable user permissions). There will be options for disabling Media entirely by default, or disabling it for specific fields by default (similar to the current per-content-type settings).

Update the per-content-type options to work with the defaults. A checkbox "Override Default" will be off to start with, and the admin can enable overrides for that content type by checking it.