BUG-1105: Implement subtree filtering in netconf

Implement subtree filtering according to RFC 6241 section 6.
Current implementation first gathers response XML, then
applies filtering. Since netconf server is pluggable,
modules that might consume significant amount of time
to build their response can read the filter and optimize
their result. Even if modules do not support filtering,
their result is filtered by SubtreeFilter right before
sending out the aggregated response.

Change-Id: Ica04f8f3adfe06599e54a577fceca0508554d667
Signed-off-by: Tomas Olvecky <tolvecky@cisco.com>
Bug 225 - added support for depth RESTCONF parameter in URI

Modified RestconfImpl to prune the resulting ComositeNode tree
based on the depth parameter, if specified.

A depth of 1 retrieves just the target resource and no children. This is
a way to determine if the resource exists. A depth of 2 retrieves the
target resource and just its direct children - any child container would
be empty.

Change-Id: I44d99f9886e3837a1bb13eda84aec3c4cc6b21ae
Signed-off-by: tpantelis <tpanteli@brocade.com>
Merge "BUG-1105: Implement subtree filtering in netconf"
Merge "Bug 225 - added support for depth RESTCONF parameter in URI"