Accept quest with command instead of chat

[ghost]

Servers that handle chat using a BungeeCord plugin never receive chat events, which makes it more difficult to accept a quest because players must explicitly specify that they want to send a local chat message. Adding a command equivalent to saying yes or no would make this less problematic, and in addition the yes/no option could be made clickable in chat and set to run the respective command.

[PikaMug]

@MegaNarwhal If not already resolved, using npc GUI should make for a proper workaround as noted in #325. However, not enhancements are being accepted at this time due to the number of bugs, so I'll mark this for later.