Add tests and fixtures for AVD Creation

Change-Id: If473e33300e1a3d6dfb1f1ffc8647d2e2b01b438
Ask 4.4W users to get L-preview for LayoutLib.

Bug: http://b.android.com/73732
Change-Id: Ibbcc83f97afe45921666da3170a2a05104fd173b
Merge "Ask 4.4W users to get L-preview for LayoutLib." into studio-1.0-dev
Clarify units for Screen Dimension

Change-Id: I831369c11b0c26dd99260f34c503410f8056b5a7
Merge "Clarify units for Screen Dimension" into studio-1.0-dev
Merge "Add tests and fixtures for AVD Creation" into studio-1.0-dev
Add AVD actions and help messaging

This change adds support for wiping the userdata partition of an AVD
and enforces this wipe when downgrading system images. It also
adds automatic repair of certain device errors.

Change-Id: I0d048a93e7e70062651e51a74031bc320244bb09
Merge "Add AVD actions and help messaging" into studio-1.0-dev