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