TRUNK-4315: Validate on client side (javascript)


https://issues.openmrs.org/browse/TRUNK-4315

Users were able to create Providers by specifying both Provider Name and Person,
this violated the rule which required them to only supply one of the two.

Decided to validate on client side because on server side calling provider.getName()
when person is set will return person's full name and so it is not possible to tell if
this was set on the client side.