workflows: fix for Celery worker tasks loading

* Loads the Celery worker tasks so that Invenio Celery wrapper
  can discover the tasks.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
jsonalchemy: create_record error catching

* The marc reader and wrapper modules now catches any errors
  while parsing MARCXML with legacy create_record and returns a
  ReaderException with details.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
records: API test case addition

* In response to 5daee2f, adds a new test-case to make sure
  an exception is raised when Record.create is called with bad
  data.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
installation: Flask-Assets upgraded to 0.9

* removing webassets from the requirements as its a direct dependency.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
assets: working combined assets

* Using STATIC_MAP to distinguish between modules and external
  resources.

* Adds STATIC_URL_PREFIX for prefixing all the static files in
  production mode. Useful if you have a dedicated host for static files.

* Fixing the documentation for sphinx.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
base: documentation fixes

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
docs: invenio.ext.assets added

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>