Option to use GroupMe ACCESS_TOKEN instead of BOT_ID

[ekcom]

Enabling the user to input solely their access token would allow the app to configure the bot name, bot id, and bot avatar for them. This would also allow adding the bot to multiple groups and removing the bot from the group via messages.
The option to use BOT_ID and GROUP_ID instead could still be used.

[ekcom]

This would also make the command set name to X possible in chat.