Fixed ScannableBase.__getitem__() to correctly throw Python Exceptions.
And added unit tests for this behaviour.
Removed override methods in derived class (CoordinatedChildScannable)
that duplicate base class methods (ScannableBase).
Removed unused imports
Merge branch '8.36' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-core.git into 8.36
Merge branch '8.36'