handle responsibility at a more granular level

[GVogeler]

Currently MOM-CA handles responsibility/authorship at levels:

1. each XML-file in the atom:author structure.
2. attribution to cei:chDesc and cei:tenor via cei:front/cei:sourceDesc/(cei:sourceDescVolltext|cei:sourceDescRegest).

Some projects use a workaround by putting names into the descriptions (e.g. http://www.monasterium.net/mom/IlluminierteUrkunden/collection).

The TEI offers a global responsibility attribution via att.global.responsibility, which seems adequate to the interests of the users.

The data model can easily be moved in this direction by adding @resp as a global attribute. But it could create additional work in:

• single charter view (how to make individual responsibility visible? Add the (multiple) responsibility to the citation suggestion? Integrate the information in PDF view?)
• search (would the responsibility by a possible constraint?)
• editor (create a mode in which changes of existing data are automatically attributed to current user?)

[GVogeler]

see #136 for another responsibility issue / enhancement.