global: test suite nosification

* Makes unit and regression test cases more friendly with respect to
  nose defaults.  That is, decorates functions that are not test cases
  as such, otherwise nose's defaults would consider them when running
  the test suite.  The nosification is useful for plugging test case
  output to Jenkins.

* Fixes all the codebase except WebSubmitFileConverterTestGenerator
  dynamically generated test cases in websubmit_regression_tests.py.

* Note that it is now possible to run unit tests like:
  `nosetests /opt/invenio/lib/python/invenio/*_unit_tests.py`
  and regression tests like:
  `nosetests /opt/invenio/lib/python/invenio/*_regression.py`.
  This gives equivalent results to `inveniocfg --run-unit-tests` and
  `inveniocfg --run-regression-tests`, respectively, modulo dynamically
  generated WebSumit tests mentioned above.

* Also, activates WebComment test cases that were accidentally
  commented out in 231caa6b80a41ad9a6b37f5bf7ddb142190742ed.