clean up from review
Push update/remove management into ExtensionManager
Removes methods that simply delegate to ExtensionManager
Incomplete: pulling the update/remove action into the Dialog.

The tests have not yet matched the refactoring, but the idea is
to have the extension manager dialog trigger the update/remove
functionality, rather than the individual views.
Addresses review comments and detects updates.
Change synchronizeRegistries to synchronizeEntry for clarity
updateFromDownload has moved to ExtensionManager
Err, the correct fix for updateForDownload
Merge pull request #4441 from adobe/dangoor/registry-model2

Registry model updates