DocumentsUI: Allow open files instead of URIs

Check files' real path and mime type to open them only in standalone mode.
This allows, for example, installing apks.

Change-Id: I4501c694db84b8595cd3928752254a8914539972
Merge "DocumentsUI: Allow open files instead of URIs" into kitkat
Merge branch 'kitkat' of github.com:AOSPA/android_frameworks_base into kitkat

Conflicts:
	packages/DocumentsUI/src/com/android/documentsui/DocumentsActivity.java