settings: Remove ZRAM settings

 * Android has proper ZRAM support builtin now, and this code doesn't
   even work. Remove it.

Change-Id: I39cb20809d5c71683bffc578057ad39363c5066e

Conflicts:
	res/values-it/cm_arrays.xml
	res/values-it/cm_strings.xml
	res/values-zh-rCN/cm_arrays.xml
	res/values-zh-rCN/cm_strings.xml
	res/values/cm_strings.xml
	src/com/android/settings/cyanogenmod/MemoryManagement.java
DeviceInfoSettings: Use ro.cm.display.version instead of ro.cm.version

Follows the same logic as ro.build.display.id/ro.build.id:
engineering, debug and unsigned builds will have no distinction,
user and signed builds will show a simplified version

Change-Id: I713ccb2445ea2e333e831129ef7733fd518282eb

Conflicts:
	src/com/android/settings/DeviceInfoSettings.java