BibEdit: support DESY author input syntax

Originally on 2012-02-07

It would be useful for BibEdit to support DESY author input syntax. E.g. cataloguers could open text input area for authors in their favourite editor and write there the following format:

```
Author1; Author2; =tag1; Author3; =tag1; =tag2;
tag1= Inst1; tag2= Inst2;
```

upon which BibEdit would parse this and would create the following fields:

```
100__a:Author1
u:Inst1
700__a:Author2
u:Inst1
700__a:Author3
u:Inst1
u:Inst2
```

Here, Authors are usually Name, Firstname or Name, I., Insts are usually DLU but could be ICN (everything with /\w+= / is an ICN), tags can be anything, usually numbers or aff1.

Start by locating BibEdit's author input handling and parser entry point. Use the DESY syntax and the example output as the behavior to verify, including author ordering, tags, and institution assignments. Done means the shown input produces the listed 100__a, 700__a, and u fields.

Written by the indexing model from the issue text.