WebStyle: fix blueprint loading refactoring issue
WebStyle: fix blueprint loading refactoring issue

* Fixes an issue introduced during refactoring from pluginutils to
  importutils loading of blueprints.

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>

tiborsimko/invenio,inveniosoftware/invenio,tiborsimko/invenio,inveniosoftware/invenio