View source for XNAT Discussion

Things we could do:

* Pull out the XNAT data structures from the plug-in and create a CTK library (there have been requests for that)
* Use virtual methods in ctkXnatObject subclasses for fetching the data (i.e. move the fetch methods from ctkXnatConnection to the subclasses)
* Support asynchronous operations in ctkXnatObject?
* Support editing Xnat data and committing it back to the servere (?)
* Think about user access rights and how to handle read-only access within setters of ctkXnatObject sub-classes
* Use ctkException as a base class for ctkXnatException
* Create (asynchronous) Qt models for displaying data in list and table widgets
* Thinks about possibilities to generate GUI masks for editing or creating XNAT data objects
* Add a simple example application which reuses Xnat related Widgets from a (new) CTK library and allows to query a Xnat server

qRestAPI library:

* emit resultReceived signal in the qRestAPI class