Restore lazy loading of LoadedApk resources

This was broken in 8fff544ec349593cfa61ae2f5ec59419fff666b6. Since that change,
resources are always initialized in getPackageInfo(), even if they haven't been
loaded before (mResources == null).

It shouldn't be necessary in *any* case to preload the resources at this point.
Anything using the resources should call LoadedApk.getResources(), which will
initialize them just when needed. Setting mResources to null resets the cache
and will force a reload the next time the resources are requested.

Change-Id: I9bc9986297478e99752b1e2b9bd04dab3dcc9656
AudioService: Show safe volume panel for non-interactive volume adjustments

If safe volume is active, apps calling mp.setVolume() to adjust the
headset to a value higher than the threshold will have the operation
fail silently because no volume dialog is active to pop up the
"do you wish to override" question.
This is particularly bad for peripherals that use the audio jack
(Square readers, Jawbone bands), since they usually require levels
close to maximum for proper communication and the app isn't prepared
to deal with a silent rejection of the requested volume.

Change-Id: I2047d199506106a87841b8b680007c5ab45b527b