Better expose 'QS Tiles and layout' function

Reorganizing & customizing the QS tiles is one of our features, but it
is buried 4 clicks deep in Settings menus. This is not ideal.

Create a new icon on the main QS panel view to quickly launch into
the configuration page.

Screenshots: http://imgur.com/a/H3iN7

This respects all the existing flip animations and quick pulldown. Does not
interfere with the clear-all button either.

PS2: Rebase
PS3: Change intent
PS4: Add missing boolean
PS5: Whitespace & Use different icon
PS6: Address comments and add additional drawable densities
PS7: Fix reference to old drawable
PS9: Swap back to + icon
PS10: Typo

Change-Id: Ia715767ba2a7cfdd44b0fafa082877def6867440
storage: Don't list removed volumes in storage list

 * Don't tell apps that USB storage or empty SD slots are available for
   use. This fixes errors about trying to create dirs in vold as well
   as the relevant CTS cases.

Change-Id: Ic763d40c19b0bb9f7497cc1515baf1661d76e9ee