Add untested code for registering a scene to a script.

This feature is required in order to have persistent scene nodes which is in turn a requirement for scripting integration.
Fix a bug where the toolbar was aligning children vertically instead of horizontally.
Add preliminary support for "playing" the scene in the scene editor.

Main purpose for this right now is testing the scripting integration.
Add shell ScriptLibrary class.

This is a static class that is responsible for loading script files.
Add shell ScriptDefinition class.

This class is going to contain information about a loaded script asset. Such information will include public attributes and the original script string.
Add the ability to acquire and unacquire script definitions from the script library.
Comment cleanup.
More work on scripting.

This is mostly just miscellaneous work on the scripting system. Still not yet functional.
Have the scene instantiate and uninstantiate nodes with script components as they are added and removed.
Have the scene unregister itself when it is destructed.
Add infrastructure for having script definitions keep track of whether or not they define certain events.

The only event tracked so far is OnUpdate().
Add serialization and deserialization to ScriptComponent.
More general work on the scripting system.
Change an implementation detail in ScriptComponent.
More fixes to ScriptComponent.
A few more fixes to ScriptComponent.
Silence a log warning.
Finish the first phase of scripting integration.

There is still a lot to go with this including integrating public variables with the editor GUI. Also need to do more event and automatic reloading.