rfe10621: improve HTTP layer exception handling

<release-note>
rfe10621: improve HTTP layer exception handling

With this change, the Java client's HTTP layer houses its exceptions
in a com.franz.agraph.http.exception package, and throws subclasses
of AGHttpException to higher layers such as the repository and jena
packages.
</release-note>

make prepush passes
make javadoc runs clean
ant tutorial runs
ant jena-tutorial runs
ant jena-compliance-tests pass

Change-Id: I1434237a12786f7ba3b531f38e70d6a1b229441b
Reviewed-on: https://gerrit.franz.com:9080/1556
Reviewed-by: Kevin Layer <layer@franz.com>
Tested-by: Kevin Layer <layer@franz.com>