WebDeposit: uncook json functionality addition

• Adds uncook functions to WebDepositForm and WebDepositField.

• Changes configuration in order to work with recjson keys instead of cooking functions.

• Adds uncook function for files based on recid using BibDocFile.

• Refactors config_utils with parse_config helper addition.

Signed-off-by: Konstantinos Ntemagkos <konstantinos.ntemagkos@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>