* Rename middleware to plugin
first pass; mostly used 'sed', few spots where I manually changed
text.
This still builds a coredns binary.
* fmt error
* Rename AddMiddleware to AddPlugin
* Readd AddMiddleware to remain backwards compat
Split up the handler_test in four files that all tests their specific
bits. Removed the CNAME sort as there was only 1 answer with a CNAME
and that was a single one.
See #942, this fixes (a bit) the tests in middleware.