Add gson support to policy-endpoints

Add gson support to policy-endpoints

Added "provider" property to both http client and server builders.
The provider defaults to jackson, to maintain backward compatibility
until other policy code has been converted to gson.
Removed commented item from pom.
Added some comments and re-arranged a few pieces of code.
Fixed a few typos and removed spacing at the end of some lines.
Reordered imports.
Added comments about limitations when using jersey-media-json-jackson.
Address ridiculous checkstyle complaint.
Support comma-separated list of serialization providers in jersey client.
Disabled metainf discovery from jersey client and server so that the
media-json dependencies could be re-instated in the pom.
Address another ridiculous checkstyle complaint.

Change-Id: Ic5a93b475d0ee9b435352b3516de6b865b00a86a
Issue-ID: POLICY-1428
Signed-off-by: Jim Hahn <jrh3@att.com>