Parameter values should consistently allow for Expression Language

The User Guide claims that Parameters cannot make use of Expression Language. And if a processor/controller service uses

context.getProperty(DESCRIPTOR).evaluateAttributeExpresssions().getValue(); 

It does, in fact, not evaluate EL.

However, UpdateAttribute uses a different API (ProcessContext.newPropertyValue(...) ) and in the API it DOES evaluate EL. We need to be consistent in how we are evaluating (or not) the Expression Language.

We do see use cases where allowing Expression Language within Parameters will be very useful, so I would lean toward allowing EL to be used. This will require that the User Guide also be updated to clearly explain the context in which the EL will be evaluated.