More support for embedded PlayN.
More support for embedded PlayN.

This introduces Config.embedded which causes PlayN not to automatically listen
for lifecycle events. The containing app must then call IOSPlatform.activate()
and terminate() to manually manage the lifecycle of the embedded PlayN game.

While the embedded game is active, it will automatically handle
background/foreground lifecycle events, and will also do the right thing if the
app is terminated while the embedded PlayN is still active.

threerings/playn,ruslansennov/playn,ruslansennov/playn,threerings/playn,threerings/playn,threerings/playn,ruslansennov/playn