Added onPause() and onResume() to SoundManager

This fixes some of the issues where AE-based games
are playing sound after leaving the game.
Merge pull request #215 from nazgee/for-nicolas-sound-pool

Added autoPause() and autoResume() to SoundManager.
Extracted ActivityUtils.showDialogOnUiThread to static DialogUtils.showDialogOnUiThread.
Making use of MIMEType enum in MailUtils.
Fixed @see javadoc not properly linking URLs.
Added Apache v2 LICENSE.md file.
Added GooglePlayUtils.
Made WifiHotspotState inner class static.
Fix for pre ICS devices also having wifi AP states of > 10. (Note: Not changing the initial condition yet, since it's so far only an assumption.)
Added MathUtils.random(int pMax).
Added IllegalClassNameException.
Moved Experiment stuff to AndEngineServerExtension.
Unified copyright.
Merge remote-tracking branch 'nicolasgramlich/GLES2-AnchorCenter' into HEAD