Moved the connection pool to a top level class and started to add more code. Still...

Moved the connection pool to a top level class and started to add more code. Still missing is evicting kept-alive connections and
queueing to limit the number of active requests per host ( and probably more ).
Started to make spdy more like a part of a http request - i.e. upgrade if supported by both ends, etc.  Now load
tests seem to work - no more OOM. Due to compression spdy it's using more memory per connection, current tests don't enable compression
( it's accepted for incoming connections ).

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@898619 13f79535-47bb-0310-9956-ffa450edef68