* 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
Fix the delegation handling in the *file* and *dnssec* middleware.
Refactor tests a bit and show that they are failling.
Add a Tree printer, cleanups and tests.
Fix wildcard test - should get no answer from empty-non-terminal
