deposit: fieldlist wrapped to a prototype based class

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
deposit: filedlist plugin separation

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

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