Revert "PIE: Improve assistant handling"

This reverts commit 32f18553a81cc7f7fd0731d13a7f26fea6e38f51.
Implement DocumentsProvider.createDocument and deleteDocument

Fixes AOSPA-431
This is needed to delete and create files/folders in DocumentsUI.
Some open questions are:
1. Are the methods implementented according to their description?
E.g I'm not sure whether deleteDocument should be able to delete folders, too.
2. I first didn't want to modify public API, but deleting files from within DocumentsUI somehow doesn't work - file.canWrite() always returns false
3. So is modfying the API this way OK?

Change-Id: Ie3a9d1888decaa0f08de1a5183ffd23760be15b9
Revert "Themes: Fix wallpaper chooser crash"

This reverts commit 7cca08daf6eb4f362a7b43763bc4675bf44a9874.

Reverted commit removed Theme Engine's dependencies. The NPE isn't reproducible for me (N4),
also i added back the missing permission that here was restored:

https://gerrit.paranoidandroid.co/#/c/4472/

Change-Id: Ie061ad72350dc10d3302791d2b7e037fa048d3c9
WallpaperCropper: Add missing Theme Engine permission

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>