JERSEY-2229  Upgrade ApacheConnector to use Apache HttpClient 4.3.x.

 - Updated HttpClient to 4.3 (4.2.5 -> 4.3)
 - Updated sse-item-store-webapp example which uses ApacheConnector.
   Removed reference to run-external-tests profile which does not exist in the project pom for the example.
 - Removed the redundant jersey-client dependency in ApacheConnector module.

 Michal:
 - Review changes + removed CLIENT_CONTEXT property.

Change-Id: Ia3a222b1d47d66c8abbc7829ee6395fb24d480df
Signed-off-by: Michal Gajdos <michal.gajdos@oracle.com>
Merge "JERSEY-2229  Upgrade ApacheConnector to use Apache HttpClient 4.3.x."