Allow custom ref types + custom default fields

Some people (well, I am one of them) may regularly deal with obscure archival or other materials in other languages that do not neatly fit into the existing default fields.

Please allow us to either:

  1. Create custom reference types (maybe easiest solution)?
  2. Permanently modify the default fields that show up in existing reference types.

In the current situation, it appears that one must manually add additional fields to the closest reference type.