[XDSB-131] Add Imaging Document Source implementation
[XDSB-131] Add Imaging Document Source implementation
[XDSB-131] Add Imaging Document Source implementation.

Add URL config attribute to XDSiSourceCfg and use this URL in XCA-I Initiating and Responding gateway to get URL for imaging source. (the previous use of getURL of XdsSource DeviceExtension is now a fallback if device has no XDSiSourceCfg device extension)
[XDSB-131] Add Imaging Document Source implementation.

Add Imaging Source to distribution.