ContentResponseHandler to extend AbstractResponseHandler

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1643670 13f79535-47bb-0310-9956-ffa450edef68
HTTPCLIENT-1583: optional connection eviction thread for non-shared connection managers to pro-actively evict expired / idle persistent connections from the connection pool

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1643671 13f79535-47bb-0310-9956-ffa450edef68