workflows: revamp testsuite
workflows: revamp testsuite

* Implements a renewed testsuite for workflows with better coverage
  overall.

* Moves the workflows and widgets loading to use registry. Tests
  also use their own test registry.

* Test specific workflows are now moved to the testsuite.

* Cleans up the tests a bit, renaming and moving the tests in
  test_halt into the renewed test_workflows suite.

* Makes the tests visible for the overall invenio testsuite by
  adding the TEST_SUITE variable.

* Fixes an issue with the custom Log handler and inheritance.

Signed-off-by: Jan Aage Lavik <8d55e006a1b29770f275a5c59a7341f17f8e69d5@cern.ch>

inveniosoftware/invenio-deposit,inveniosoftware/invenio-deposit,inveniosoftware/invenio-deposit,inveniosoftware/invenio-deposit