Remove empty vendor package from openspending
Fix openspending versioning (and update to 0.12.0)

We had two different versions for openspending set at the same time.
One was set in the conventional openspending/__init__.py file (just
recently added) while the other was set in the
openspending/version/__init__.py file. In openspending/__init__.py
the version number was 2.0 but in openspending/version/__init__.py
the version number was set as 0.11.

This implements Zooko's convention of version declarations. That
means the version file should be called openspending/_version.py
and contain the __version__ attribute. This should then be
imported by openspending/__init__.py but setup.py needs to parse
the version number from the version file with a regular expression
(this avoids executing the file).

Since the home controller has a method that returns the version
that controller needed to be updated as well.

Since we're playing around with the version, we can update the
version (which hasn't happened in a long time) which is now
0.12.0 (going to 2.0 is too big of a step).
Fix test package filters so that it include openspending.tests

We still exclude test cases but want to find packages which provide
test functionality (in openspending.tests.base and
openspending.tests.helpers).