NEXUS-5739: Remove HC3

Removed HC3, RRS imple using it and related
tests that were testing HC3 RRS or the customized
CustomMultiThreadedHttpConnectionManager for
connection leaks and non-proxy-host support.

Still, legacy ITs nexus-test-harness-launcher
still has it as dependency, as many
legacy "clients" and "message util" classes
has direct dependency on it.

At the end, HC3 is out of the bundle, but
is still used by legacy ITs only.
Merge remote-tracking branch 'origin/master' into remove-hc3
NEXUS-5732: Remove HC3

HC3 removed from OSS ITs too.
Fixing bugs.

Mistakes made during HC3 to HC4 change.
NEXUS-5732: Fixing NPE in IT

Restlet Client using j.n.URL behaves slightly
differently that HC3 powered one (that is gone),
so simple fix to get rid of the NPE: body is null
with j.n.URL client.
only buffer entity if there is one.
Killing of the need for restlet1x plugin in legacy ITs

The legacy ITs were having restlet1x plugin as dependency,
while it was really unwanted.

This needed a bit of reshuffle of deps, as Restlet Client
is still used by many IT clients.

Also, some constants got duplicated (but shared, as are used in
Pro ITs too).
Merge remote-tracking branch 'origin/master' into remove-hc3
Getting rid of HC4 profiles.
Undone formatting and readability related changes.

And tuned eclipse formatter to not do that anymore.
Workaround for URLConnection caching auth.

With drop of HC3 we also don't use the Restlet Client
powered by HC3 but a fallback to one using java.net.URL.
But, that one suffers from the "auth caching" problem,
so added a workaround that clears URLConnection auth
caches for now.

Fixme: as the workaround uses sun... package,
will emit warnings, but this is the only way to
make URLConnection use different (or none after using
some) auth info in subsequent invocations against same
host/port combo.
Merge remote-tracking branch 'origin/master' into remove-hc3
Merge remote-tracking branch 'origin/master' into remove-hc3
Removing java.net.URL backed restlet Client
and adding HC4 backed one.
Merge remote-tracking branch 'origin/master' into remove-hc3
Cleanup of HC4 Client
Merge pull request #22 from sonatype/remove-hc3

[WIP] NEXUS-5732: Remove hc3