adding skeleton for WPF application
initial layout of main window elements
added animated GIF test image
implementing INPC on sprite sheets/sprites
added case for when no class name is provided
changed GetEffectiveClassName to property
added EffectiveClassName to NPC events
setting up initial commands and bindings
smarter hiding of current sprite elements

A new CurrentSpriteDependent style was added, keyed to a base
FrameworkElement, which collapses the visibility when the current sprite
is null.
consolidating ICommand code
fixed document cref
adding image path commands (browse/clear)
adding dialog/VM for displaying messages
adding saving/loading service methods
removed Close menu option
documentation
restructuring commands

There is now a new CommandBase(Of T) which will be used for sprite-sheet
(and not sprite) specific commands
better encapsulation for VM properties
info dialog can now check for errors/warnings
added helper TryExecuteHandler method