add /vendor support

- look in /vendor/firmware/... in addition to /system/etc/firmware/... for firmware loading
- add /vendor/bin to path before /system/bin
- add /vendor/lib to ldpath before /system/lib
- configure appropriate permissions for /system/vendor/bin
- symlink /vendor -> /system/vendor

Change-Id: I0c06ca1e38a44f0c7024cee6cea8907aa93a4532