DS favourite places

Docking Station introduced a new, more easily extensible system of favourite places, in order to make it easier for third-party addons to create consistent, non-conflicting favourite places icons. The system is documented at the CDN on Gameware's site, in the article Favourite Places in Docking Station.

The following may be useful to coders wishing to use the system:
 * The number of favourite places in the game is stored in GAME "ds_favourites".
 * Each favourite place icon (1 4 x) has the following variables attached:
 * ov00: 1 if currently highlighted, otherwise 0
 * ov01: metaroom attached to
 * ov50: position in favourite places stack (between 0 and GAME "ds_favourites")
 * Each favourite place icon has the following useful scripts attached:
 * 1 (activate): go to room
 * 1000: if _P1_ is our stack position (ov50), highlight ourselves; otherwise, dehighlight ourselves
 * After an icon is clicked, message 900 (metaroom changed) is sent from its script 1 to all agents.