ISIS-478,ISIS-503: various fixes.

ISIS_478, for conditional choices, for EntitySelect:
* clear link now should work
* if no choices/autocomplete then doesn't NPE (BankMandates#newBankMandate)
* removed ID_ENTITY_TITLE_NULL label, since never visible
* sets up a placeholder text
for conditional choices, for ValueSelect:
* correctly initializes second dropdown based

ISIS-503, for contributee actions/associations, calculate identifier
* was causing stack trace when go back to list, caused by call to getIdentifier() incorrectly returning the wrong value for a contributed association.