global: new publication subtype `Proposal`

* Adds `Proposal` subtype to `Publications`.

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>
I invoked `inveniomanage upgrader create recipe -r zenodo -n new_subtype_proposal -p zenodo.base`, which generates for me the file with the dependency set to `zenodo_2014_02_04_old_tables` (still not the right one). 
Is there sth wrong with the command ?