Added some placeholder art
Mixed bag of changes

* Added a basic texture
* Added the locations of previously declared textures
* Added some new texture names
* Told initialize assets to load some new assets
* Added a load splash function, and a unload splash function
* Switched command to its own file
* Fleshed out the menu header to prepare for menus, menus now have a
vector of selects, which hold functions that lead to other menus. The
game now has one active menu, where  it will apply future input info.
Deny lets you go to previous menu, confirming confirms whatever is
selected.
* Added a tilespath
* Changed main to have the actual function to start the game, but it
obviously remains commented out
*