CORE - Add checkForException in ScanDataPointPipeline

The main Scan thread can check this regularly
CORE - AbstractContinuouseScanLine - tidyup ScanPositionRecordable types

Check for exceptions in ScanDataPipeline during the controller move
CORE - Extension of ConstantVelocityMoveController

Extension of ConstantVelocityMoveController that requires knowledge of 
scannables and detectors
The start, and stop values are the values around which the exposures
are to take place irrespective of whether the detector is integration or
not
Core - Support ConstantVelocityMoveController2