Fixed "CameraController not in motion" errors.

These occurred when the user accidentally moved the mouse scroll wheel while performing a drag to move the camera. We now ignore wheel events when dragging the camera.
Removed unnecessary collapsible section in Group UI.
Merge branch 'master' of https://github.com/ImageEngine/gaffer
checking if the plug has the settable attr, checking if the paratemer has widget
Merge pull request #235 from paulondc/UiChanges

UI fixes for the parameters/plugs
Found and corrected a bug when reading images that have a data window with an offset.
Merge pull request #221 from goddardl/ImageTransformNode

Reformat Node + Sampler + Filters
Added a todo about the failing part of the test case.
Removed a line which shouldn't be there...
Merge pull request #237 from goddardl/ImageReaderBug

Image Reader Data Window Bug Fix.
Created a Transform2dPlug and it's test cases.
Changed getChild() calls to use an index from the first plug rather than by name.
Rebased and added Recursive Child Iterator.
Added inherit argument to Metadata query functions.

This defaults to True (the old behaviour), causing metadata for base classes to be returned if none has been registered for the actual class in question. Passing False causes the lookup to fail if metadata has not been registered for the exact type in question.

Fixes #232.
Renamed Transform2dPlug to Transform2DPlug
Merge pull request #234 from goddardl/Transform2dPlug

Created a Transform2dPlug and it's test cases.
Fixed a typo.
Found a bug with the way the parameters to the tbb blocked_range2d were being set.
Removed todo
Added a todo.