Alpha 19: Dropdown Menus and Better Keyboard Controls

dropdown menus and better formatting

engine changes:
-implemented dropdown menus
-menu titles can now be alligned top, center, or bottom
-changed how key toggles work
-removed object::name
-menus now have borders
-button labels can be alligned left,middle, or right
demo changes:
-relabeled the "new object" buttons and added them to a dropdown menu
-changed the "return to menu" warning
-changed the object spawn points
-pause screen may now be toggled
-updated readme