GDA-5386 (8.34) Fix TwoDScanPlotter to deregestister as an SDP listener only after recieving te last point rather than atScanEnd(). Also deregister in atCommandFailure() and stop().

Now we have multiple scan threads atScanEnd can be called before the pipeline has been emptied.
GDA-5386 (8.34) Prepare TwoDScanPlotter for extension to plot also to Swing clients (as a backup!)
GDA-5386 (8.34) Expose synchronous, exception throwing, eval() and exec() methods to JSF.

Being unable to call Jython in a reliale way was untenable.
GDA-5386 (8.34) Fix ScannableMotionWithScannableFieldsBase to work with all ContinuousMoveControllers
GDA-5386 (8.34) Fix AbstractContinuousScanLine to handle exceptions while preparing devices for collection
GDA-5386 Modify ConstantVelocityRasterScan to allow zero-input-extra-names Scannables

... refactor and create test code for existing argument checking.
GDA-5386 Create a ConstantVelocityRasterScan