[KFSQA-649] Refactored AccountingLinesMixin et al. to move out rarely used fields into their own mixins.
[KFSQA-649] Got Transfer of Funds working and fixed some visit() bugs in existing FP objects.
[KFSQA-649] Got Internal Billing working.
[KFSQA-649] Got Distribution Of Income And Expense working.
[KFSQA-649] Started work on Auxiliary Voucher.
Merge branch 'KFSQA-649'
Temporarily changed a @wip to @pending.