Create unique files, root ordering, UI bugs.

When a file already exists on disk, try adding a counter suffix to
make a unique name.  Move services near top of roots list, just below
recents.  Remove "Documents" root.

Increase number of recents allowed from single provider, and add more
logging to diagnose wedged loaders.

When launching GET_CONTENT apps, wait for successful result before
relaying result; canceled requests now return to DocumentsUI.

Add CloseGuard to ContentProviderClients, since leaked instances can
keep the remote process alive.

Fix UI bug around trailing breadcrumbs.  Fix bug that dropped Recents
from roots list.  Add up action to Settings activity.  Give our
activity a default icon while waiting for async roots to load.

Bug: 10818683, 10819461, 10819461, 10819196, 10860199
Change-Id: I7b9e26b1cf8353dd3175458b23da2b4bda6c5831