jsonalchemy: exception messages improvements

* Passes detailed parsing error message

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
deposit: missing super() call in a template

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
records: base variant of base.html

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>