add mruby on apps

Add mruby on apps, support make all image=mruby.

Reviewed-by: Tomasz Grabiec <tgrabiec@gmail.com>
Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

apps @ 23edda60

-Subproject commit 1dfe6accad74f25d7d0b960de2921bb6615bc12a
+Subproject commit 23edda60e214f745615b776d529aa0d27ed2195c

images/mruby.py

+from osv.modules import api
+
+run = [ api.require('mruby').default ]