Aura/ESP updates

[Rias]

From the changelog:

- Auras can now only be selected with the assistance of the Twilight Eye. Check the second floor of the local Town Hall for the Twilight Eye Services office. Various in-game command messages have been updated to indicate as much and guide players.
- There is a new tutorial task for finding the Twilight Eye Services office and choosing a specific aura.
- Worn ESP artifacts will no longer transmit messages for characters with the default Gray aura. Stationary ESP artifacts will still work for those with Gray auras.
- It is no longer possible to choose Gray as one's aura color. (It remains the default.)

This should make the overall concept and implementation of auras a tad less meta/OOC. Still nice and mysterious though, being tied to those cagey Twilight Eye mystics.