[JBIDE-13763] added requested url to exceptions

changed exception construction in UrlConnectionHttpClient to
always contain the requested url so that the server that we
were talking to is shown.
RestService#request reports full URL (not path) when throwing
fixed proxy handling

Removed the proxy parameters from OpenShiftConnectionFactory
which implemented an unexpected behaviour where it would
set the proxy in the system properties. Replaced it by pom
directives that would instruct maven to read the
integrationTest.properties and set it to the system properties.