Pass in dependencies to ServerManager explicitly.

Avoid static/singleton references, and use a temporary Provider<>
implementation that will eventually be replaced by Dagger.

Change-Id: Id1bda9437f71cc9ddceb0a9ed1ba38d4787f2226
Reviewed-on: http://gerrit.dmdirc.com/2671
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager