Enable ro.config.low_ram to indicate low RAM device

Change-Id: I51dde0b745b2a18d24f32162f485d5fad69e1526
Update permissions for /storage on Android 4.4

As of Android 4.4, sdcard_r is no longer required to access limited
parts of external storage, so 0050 permissions are no longer
appropriate.

Change-Id: I99b0041453aef0a402edf3c65d9ea9a0f0aec227