Configure dalvik heap parameters for low memory devices

Reduces after boot memory footprint by about 5-8MB
Note: This is for low memory based devices only (~512MB RAM
or less)

Change-Id: Iac45854aff687189e56f97da96e05d38adf842bf
Merge pull request #1 from omnirom/android-4.4

Configure dalvik heap parameters for low memory devices