* 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
* add wildcard parameter to allow resolving multiple name to the same IP
* first test for the reverse wildcard middleware
* update wildcard keyword test to pass code coverage