Content system

Requirements for interface to engine:
*   Variables can be linked to options (or get and set)
*   Callbacks can be set for events: when variables are set and "click events" (e.g. buttons)

Requirements for within-gui content handling:
*   Services acting on content, e.g.:
	Clipboard (copy/paste)
	Spell-checker
	Widget editor (for gui-editing if widgets are handled as content)

Content-Options interaction:
*   Combine the two?
*   Or link them?
	Content can be linked to individual options, setting them
	Content lists can be linked to option lists

Content-Gui interaction:
*   Gui can get content
*   Gui can set content
	triggers content event callbacks
*   Content can cause a re-get/re-draw of widgets using their content?
*   Gui list-widgets can be associated with content lists

Content system:
*   Content variables/lists can be created by engine or gui (or loaded as generic options?)
*   Use options-like approach with named-variable support plus generic variable support (if not named, revert to a dynamic array for storage)
*   Support arrays and possibly other data structures