WebStyle: option to disable loading of blueprints

* Add new config option CFG_FLASK_BLUEPRINT_DISABLE which takes a
  comma-separated list of blueprint modules which should be disabled
  (i.e. not registered with the Flask application).
BibDocFile: fix for instantiation of BibDocFile

* BibDocFile was recently refactored so that it no longer takes a
  doctype parameter on initialization. However the function
  generic_path2bidocfile was still wrongly initializing BibDocFile
  with the this parameter (closes #1317).