Previously we always load android.img from server when building snap.
Now, build with <ANBOX>/android-images/android.img if there is one.

 * Don't crash inside AlarmManager when PendingIntent is not set

Changes:

 * Android system log is now dumped into $ANDROID_DATA/system.log so
   it can be accessed without adb and logcat
 * Fix SEGV in art on newer kernels with CVE-2017-1000364 fixed

Fixes #337

As both kernel modules are not part of the standard Ubuntu kernel we
need to build and load them at runtime. We bundle this together with
the container manager start and reuse the classic snap scripts to do
the actual build in a proper environment.

Mount /cache and /data properly and stop bridge correctly.

If we run the management process with the AppArmor profile loaded
from snap-confine various ashmem/binder operations are failing with
permission denied errors. To workaround this until this problem
is fixed we simply unload the AppArmor profile and continue to
execute completely without any profile loaded.

We have adb now available and kernel module support need to be solved
differently.