* 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 auto-load middleware that automatically picks up zones.
Every X seconds it will scan for new zones.
Add tests and documentation.
Make 'make test' use -race.