Sandcastle tweaks

Added the below two functions to Sandcastle and made the relevant demos include them.

1. `Sandcastle.addDefaultToolbarButton` executes and highlights the toolbar immediately, eliminating the need for breaking out an extra function to call (muddying the code in the process).
2. When defined by a demo, `Sandcastle.reset` is called whenever a button or menu selection is main.  This allows for the bookkeeping/cleanup code to be cleanly abstracted away from the example-specific code that the user is interested in.