jsonalchemy: fixes for versionable extension

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
documents: checker of source and uri addition

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
documents: test improvements

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
jsonalchemy: cache engine addition

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
travis: travis_retry statement for grunt

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
scheduler: tasklet registry addition

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
jsonalchemy: default values for subfields

* Fixes jsonalchemy ignoring default values when the main field is
  present but not one of the subfields. (closes #34)

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
assets: fix some missing url_for("static")

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
Reported-by: Jan Åge Lavik <jan.age.lavik@cern.ch>