Add more BIBO types

Source:
http://biblatex.dominik-wassenhoven.de/download/DTK-2_2008-biblatex-Teil1.pdf
pp. 18-19
Add support for pagination in DC source

Source:
http://biblatex.dominik-wassenhoven.de/download/DTK-2_2008-biblatex-Teil1.pdf
page 17
Add more thesis types
Add DC identifiers
Add bibo publisher
Add DC isPartOf
Add keywords
Refactor Entry#to_citeproc by introducing Entry::CiteProcConverter