Update inSampleSize calculation - while this didn't affect iosched the existing
formula would calculate the wrong value in some cases.

Unpause the image loader when the activity/fragment is paused - the image loader
is paused while flinging the social stream fragment, however if the activity is
destroyed while the image loader is paused this can leave the background thread
in a hung state.

Change available app memory calculation from memory class to available runtime
memory - used to set the image memory cache size.