* 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
There was quite some code duplication in a lot of tests to check if
an answer was considered Ok. Created a test.SortAndCheck helper function
that takes care of this.
* middleware/file: don't reload zone when SOA isn't changed
Give Parse an extra argument which is the SOA's serial, if > 0 we check
against the just parsed SOA and then just return.
Most notable use is in reload.go which is both used in the file and auto
middleware.
Fixes#415
* PR comments
