NIFI-3122: Do not validate component types in template anymore. Inste…

[markap14]

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…ad, just allow Ghost components to be created

[mcgilman]

Will review...

[mcgilman]

Before we can remove this check I believe we need to provide support for ghost Prioritizers. Otherwise, if a template references a Prioritizer that doesn't exist in this NiFi instance we would throw an exception when instantiating the Template.

Alternatively, we can keep this part of the verification in place. However, I think the ghost Prioritizer would be the preferred approach.

[joewitt]

@markap14 @mcgilman can we get this closed out or pushed across?