Merging ub-launcher3-master, build 5294095

Test: Manual

Bug:120559294 Create a Customization section Fragment for Themes
Bug:122524192 Create release process for ThemePicker/WallpaperPicker2/WallpaperPickerGoogle
Bug:123648086 ThemePicker: Grid section flickers when choosing each option
Bug:123904588 Use ContentProvider for clockfaces instead of a stub
Bug:124071372 Respect current theme's rounded corner in ThemePicker

Change-Id: I4d18f2d59f4fc313756e32a7542f0191dc760ac8