collect: addition of filter for Blueprints

• Upgrades to Flask-Collect>=1.1.1. (closes #2353)

• Adds DeprecationWarning to Invenio link storage.

• Updates .travis.yml.

• Updates documentation.

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