perf(nifi): Speed up build

[NickLarsenNZ]

Add additional maven options to skip unnecessary compilation.

• skipTests (already done, and used as inspiration)
• maven.javadoc.skip=true (don't generate docs)
• enforcer.skip=true (skip environmental dependency and constraint enforcement - maybe we shouldn't skip this?)

  like to know if a patch of ours breaks one of the enforcer rules

• maven.site.skip=true (skip generating the project site)
• T 2C (build with two threads per core. I tried 1C, but it didn't appear to help).

[NickLarsenNZ]

Before:

sample 1	sample 2	sample 3

After:

-T 1C	-T 2C
Not much of an improvement	Pending
	TBD