First commit for settings panels

Establish the Activity which hosts Settings panels through the
PanelFragment. The Activity's purpose is to validate the intent
data coming in, including:
- Called with startActivityForResult (so we can log who is calling)
- Intent has the proper intent extra to link to a Panel

The fragment takes the Panelable data and builds a Settings Panel.
Each panel will have:
- Title
- List of Slices
- Link to underlying content

The Panelable interface is created to provide all of those datums, and
the new FetureProvider provides the Panelables by linking them with
keys. The keys will eventually become public APIs with CTS tests.For
now, we store them locally.

I included an exmaple panel, the InternetConnectivityPanel which
currently shows Wifi and Airplane mode.

Screenshot: https://screenshot.googleplex.com/c6sv7ZzQ5OJ
Bug: 117804089
Test: make -j40 RunSettingsRobotest
Test: Manual app
Change-Id: I1932f7179cc32088acd6413a736901ddf9651892