shift-axolotl: add support for dynamic partitions (MR 3137)

For more information, see this wiki entry:
  - https://wiki.postmarketos.org/wiki/Android_dynamic_partitions



Change-Id: Iaf4ba715bc7226d43e05213cd5bd6ce82d327b7e
Signed-off-by: Alexander Martinz <amartinz@shiftphones.com>