installation: MANIFEST template fix

* Fixes the MANIFEST template to include all jsonext configuration
  files.

Co-authored-by: Esteban J. G. Gabancho <egabancho@gmail.com>
Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
jsonalchemy: Versionable test addition

* Fixes @connect decorator by adding implicit @parse_first
  rule for connected field.

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