collect: addition of filter for Blueprints

* Upgrades to Flask-Collect>=1.1.1 (addresses #2353)

* Removes custom Invenio link storage (now part of Flask-Collect).

* Updates .travis.yml.

* Updates documentation.

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>