deposit: js - Filter -> Mapper name change

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
deposit: mapper.js - documentation improvements

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
deposit: data source concept

* Separates data sources as a plugable objects
  for deposit import.

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