InvokeHTTP is a Final Class

[Devin Fisher <de...@perfectsearchcorp.com>]

I was looking at using InvokeHTTP as the base for a class that would
interact with our API.  I wanted to to have the processors make some
assumptions that are true with our API but not HTTP in general (Mostly our
method of Authentication). This class looked well suited for this (the
class is well decomposed with methods that deal with different aspects of
HTTP Protocol). But the InvokeHTTP is a final class which prevents me from
using it this manner.  I have looked over the StandardProcessors and this
is not only one that is a final class. So I was wondering if there is a
reason for this. And if not if it could maybe be changed.

I'd be happy to make the change. I have been meaning to figurate out how
contributions are made in the Nifi community. This might be good chance to
figure that out.

Devin