WebDeposit: form status & ui actions on fields

• Adds a for status indicator woth Saving/Saved indications.

• Renders additionally the description of a WTField as a helper.

• Adds hide/show/enable/disable functionality to be performed on fields upon validation. The actions can be configured in the returned dict of validating functions.

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