Handle resetting traversed nodes correctly for /completionist mode.

Cached the *actual* traversed_nodes when entering map selection before adding all nodes to traversed_nodes for /cyoe mode, restoring the actual traversed_nodes when leaving map selection. This allows other modes (like Peregrinaje) to read reasonable numbers of traversed nodes instead of keeping track themselves.

Choose Your Own Expedition mode works for clients now (still must be enabled by the host).

/cyoe mode not quite working for clients.

Added "Choose Your Own Expedition" (/cyoe) mode.

Initial stable version.