Add missing auth headers to guard request

Add missing auth headers to guard request

Added guard authentication, client authentication, and environment http
headers to the pdp-x guard restful request. Properties are set to
PolicyEngine.manager. Property getter, setter, and properties in
guard/.../Util.java. Test properties defined in junits themselves. Added
code from GuardContext.java to grab the properties and make restful request.
PolicyGuardXacmlHelper now closely resembles GuardContext in order to mimic
functionality. Guard url no longer is passed into CallGuardTask, it is now
a property.

Issue-ID: POLICY-260
Change-Id: I5b144764828b6da0e7b738a578e4f6596a0f4f36
Signed-off-by: Temoc Rodriguez <cr056n@att.com>