sipcreator - add accession option

[kieranjol]

This combines the OE and accession process in the cases where:

• QC has already been carried out
• The files are definitely going to be accessioned.
• an accession number and a OE number are pre-block booked
• the filmographic already exists

This also generates a helper OE record that fills in OE number, title, accession number, acquisition info, and it automates the 'Representation of X|Reproduction of X'.

It should significantly reduce the admin required for object entry-ing/accessioning objects that we know will definitely be accessioned.

Some extra checks need to be added - like an initial check to see that the reference number actually exists in the filmographic.

Feedback very welcome @raecasey @ecodonohoe .

[kieranjol]

It also makes sense to check that the -csv option is used alongside -accession as both are necessary. I think i had problems in the past trying to force a second option if one option is used in argparse, so perhaps just prompt the user for the path instead.

[kieranjol]

It's easy to use mergepbcore to make the database import CSV, but generating all the accession register records can be a bit trickier as they are now all individual files.
I have a workaround where i use bash tools like cat and sort to make the helper file which is all fairly painless, but something else might need to be added in python.