Fixed unnecessary test failure in RenderManLightTest.

It was broken by 0602be75a59fa0ef901953bb03f04ba039dbd834, where ExecutableRender stopped saving the script and instead deferred to Dispatchers.

Also removed outdated comment.
Added OpDialogue preExecuteSignal() and postExecuteSignal().
Added OpDialogue.parameterisedHolder() method.

This may be used to edit the parameter values.
Reordered GafferUI.Window methods.

There was private implementation stuff right in the middle of the public API.
Merge pull request #910 from johnhaddon/opDialogueCustomisationHooks

OpDialogue customisation hooks
Improved diff formatting in SceneInspector.

Character-level diffs are now highlighted, and cell-level highlighting is applied to the tables used to display boxes and matrices.

Fixes #894.
Added options section to SceneInspector.

Fixes #197.
Improved SceneInspector formatting.

- Added specific formatting for vectors
- Added Box2 formatting
- Formatted bools as True|False
Added a flags argument to ParameterHandler::setupPlug()

This allows clients to choose the default flags for their plugs, rather than being forced to have (Default | Dynamic) plugs.
added ViewDescription constructor for 3 argument registerView
DispatcherUI calls Dispatcher::dispatch() on the main thread.

LocalDispatcher has a new executeInBackground plug and manages the background thread on its own. This is so we can do alter things before the asynchronous bit begins.

Note that while Dispatcher::postDispatchSignal() is still called after the dispatching itself finishes, it may now be called before the actual task execution finishes.
Merge pull request #918 from andrewkaufman/parameterHandlerFlags

Added a flags argument to ParameterHandler::setupPlug()
Merge pull request #919 from davidsminor/threeArgumentViewDescriptionConstructor

added ViewDescription constructor for 3 argument registerView
Merge pull request #920 from andrewkaufman/asynchronousDispatcher

DispatcherUI calls Dispatcher::dispatch() on the main thread.
Removed diff highlighting from SceneInspector node name section.
Removed highlighting from non-strings in SceneInspector.

It didn't make any sense applied to types like bool.
Improved SceneInspector numeric formatting.

- Aligned values per-column to make comparison easier
- Used a monospaced font to make comparison easier and alignment possible
- Highlighted the whole number from the first difference
- Added support for integer types
- Put transforms/bounds one above the other rather than side by side - they are too wide with the new formatting
Removed displays from SceneInspector options section.

These will be displayed in their own section instead.
Merge pull request #914 from johnhaddon/sceneInspector

Scene inspector improvements
LocalDispatcher defaults to execute in the foreground.

The gui startup config sets it to execute in the background.