Lua hooks for the comm board

[MjnMixael]

This adds a few useful features to get full access to the comm board and enhance or entirely replace its functionality.

• mn.CommItems grants access to the current menu items. This is not just 0-9 visible items but also any items that could be paged to using PgUp or PgDn. CommItems come with Name, Active (whether the item can be selected or not), getMenuTitle() to get the current title of the menu, selectItem() which selects it and either moves to the next menu or activates the order, and isValid().
• On HUD Comm Order Issued overridable hook that runs when an AI order is issued via the comm board. It comes with hook variables for the Sender, the Recipient, the Target, the target Subsystem, the Order enumeration, and the visible Name of the order as it appears on the comm board.
• mn.sendBuiltinMessage() which works exactly like the send-builtin-message SEXP