audit2allow: execute selinux tools from prebuilts

Instead of moving audit2allow into out directory, run directly from
selinux/prebuilts. Include path in build/envsetup.sh

Includes some general cleanup of the file structure.

(cherry picked from 24f9ffc47873190e82a75e989a25e21ed59416f4)
Bug: 21724977
Change-Id: Ide320a56b9cdbfa426b978443f6df07fa2a38fbc
26 files changed