cm.mk: Clean up makefile

Override CM's common_mini_phone.mk with a local common.mk, based
on the one in vendor/cm/config/.  Removes some non-essential apps
and overrides CM's dictionaries to include only the English dict,
saving ~30MB from /system.

Should be sync'd from time to time with CM's vendor/cm/config/common.mk.
overlay: Add English dictionary to overlay

See overlay/vendor/cm/config/common.mk where we override CM's own
dictionaries to save ~21 MB on /system.