Add GlAppSwitchTest

 - switches between two Gl-using apps and forces recreating GlContext
 - replica island is used for one GL app.
 - if something goes wrong and rendering is blocked, watchdog timer
    in each app will fire
 - fixed a bug in GlPlanetsActivity as the original code freed vertex /
    index buffer and did not create after pause resume
   : Buffers are just kept to reduce resume time for this test

Change-Id: Ie9f81f97f2746740c9bc37fe000a998bc4e90701