BUG-628 Allow configuration to override module based capabilities from remote netconf device

Suitable for devices that do not provide module based capabilities in hello message (most likely do not support ietf-netconf-monitoring).
User can place yang files into cache/schema folder and set the capabilities for these modules into config attribute for netconf-connector.

Change-Id: I541ef08bb5c0328e293f9c732353282ffaf0474d
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>
Merge "BUG-628 Allow configuration to override module based capabilities from remote netconf device"