Pull event handler for full import

[isc-pbarton]

Currently we have pull event handlers out of the box for an incremental load of changed items, or a full load of the package using IPM. Some users might not be using IPM but still wish to do a full load of all items in the Git repository.

[isc-tleavitt]

Note on this, we need to think about how deletes would be handled in this case.