Remove NPN support from OkHttp

Work in progress.

I see a new failure from a certificate pinning test but I don't
know why. Help solving this would be appreciated.

I also see failures before & after:
1) A failure from DisconnectTest
(https://github.com/square/okhttp/pull/1197 may fix that).
2) A failure from CallTest.doesNotFollow21Redirects_Async (timeout)

The maven changes should be treated with the contempt they deserve.
I mostly removed things I didn't understand and stroked maven until
it stopped squealing. The benchmarks / okcurl changes are a
particular mystery.

Tried with arbitrary versions of openjdk7 and openjdk8 I had
lying around. Behavior was the same across both (i.e. the same
failures).
Are you sure?

Based on:
https://webtide.com/jetty-9-2-0-released/

"ALPN is the successor to NPN (the Next Protocol Negotiation) and is implemented for both JDK 7 and JDK 8. ALPN will be used by SPDY and HTTP 2.0 to negotiate the application protocol of a TLS connection."

Various SPDY tests broke on OpenJDK 7 without this, and passed with it.