* 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
* cleanup: go vet and golint run
Various cleanups trickered by go vet and golint.
* Fix tests and lowercase all errors
Lowercase all errors, some tests in kubernetes use errors from
kubernetes which do start with a capital letter.
* Use common TLS parsing routine for etcd
Change to use the new common routine, and update the docs to reflect
the different options for passing TLS configuration.
* Move middleware/tls to middleware/pkg/tls
This was put in the wrong place originally.
