* 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
* middleware/proxy: config syntax cleanups
Allow port numbers to be used in the transfer statements and clean
up the proxy stanza parsing. Also allow, when specifying an upstream,
/etc/resolv.conf (or any other file) to be used for getting the upstream
nameserver.
Add tests and fix the documentation to make clear what is allowed.
* Fix the other upstream parse as well