archipelago: Extend v0 options to vlmc api
archipelago: Extend v0 options to the cli application
archipelago: Pass v0 options to blktap
mapper: Add MF_OBJECT_DELETED flag

Keep track of deleted objects on the mapfile, by setting the aforementioned flag
when deleting an object.
mapper: Add object delete functionality

Add mapper handling functions to delete an object. Also provide an appropriate
callback function.
mapper: Remove unused objects on removal

Remove unused objects on resource removal. These writable archipelago objects
are certainly garbage, so we can remove them eagerly when removing a resource.
vlmcd: Handle volume remove

Assert that there are no pending I/O operations on the volume when removing.
Then forward the remove request to the mapper.
archipelago: Send remove request to the vlmc

Send remove request to the vlmc instead of the mapper, to ensure proper removal
of the volume.
mapper: Do not delete mapdata on destroy. Only on rename.
mapper: Always cache readonly maps

Seperate exclusive attribute from can_cache attribute.

* Assume that readonly maps are not modified while mapped, so do not keep the
  map locked, if it is readonly.

* Assume that every readonly map can be safely cached until explicitly closed,
  without the need to hold the lock.