Update package status will re-post to LOM

refs #5425

Updating package status will re-submit the atom entry to LOM, if the
first entry failed. post_move_from_storage_service updated to be
idempotent, including all the functions it calls.

Refactored split_package to include all modifications to the pointer
file, and create_resource to only create the atom entry.  split_package
will return the output files if a split has already been performed.

Generate checksum moved to utils.  Parsed pointer file for current
Package made an attribute of Lockssomatic, populated on demand, so it
is easier for functions to reuse it.
LOCKSS AU chunk numbers from 1

refs #5425

Update download_url and download_path to both be indexed from 1,
instead of mismatched.
Delete AIP from LOCKSS

refs #6542

Notify LOM that files will be deleted, but ignore errors.  Delete split
files and original AIP from local filesystem.  _delete_files refactored
to support this.
Fix LOCKSS bugs

refs #5425

When updating service document fails, don't continue the function as
LOM is probably not accessible.  To account for earlier versions of AM
pointer file, add fileGrp USE="Archival Information Package", as LOM
processing expects it.
Update migration

Update migration for LOCKSS-o-matic table and Package.misc_attributes.