[bugfix] Removed warning fired on undefined arraySeps
Added the chance to use more than one controlled vocabulary.

XML Schema used to describe the models has been updated in order to
be able to tell that a column can have valid values from more than
one vocabulary.
BP::Model now deals with restrictions of multiple CVs

Although the XML schema allowed to declare more than one controlled
vocabulary as a restriction for a given column, BP::Model and the
tools using it (SQL generators and so) where not prepared for such
feature.
data-version label from OBO files is now acknowledged (and generated).
Merge branch 'develop' of https://github.com/inab/BP-Schema-tools into develop

Conflicts:
	model-doc-generator.pl
Merge branch 'develop' of https://github.com/inab/BP-Schema-tools into develop

Conflicts:
	lib/BP/Model.pm
Added BP-Schema-tools its icon
Migration to latexmk

latexmk is able to properly track changes on all the sources used in a
LaTeX project, and it is also able to detect whether to run again latex
or not. In this way, model-doc-generator.pl does not have to blindly
run latex, having faith on a high number of re-runs.