Schematize ADB system properties

Properties accessed across partitions are now schematized and will
become APIs to make explicit interfaces among partitions.

Bug: 117924132
Test: m -j
Change-Id: I654c0e1f234d097a66f79ba8c019b8bebc794816
Merged-In: I654c0e1f234d097a66f79ba8c019b8bebc794816