bugfix: restore setting classification source by dropdown

bugfix: restore setting classification source by dropdown

Apparently as an inadvertant result of the patches to
move the SQL files to load the MARC frameworks, the
authorised_value of 'cn_source' was dropped for
kohafield = 'items.cn_source' and 'biblioitems.cn_source'.

This patch restores those values, thus making the
classification source set by a dropdown in the bib
and item editors.

Signed-off-by: Joshua Ferraro <jmf@liblime.com>