Improve "command not found in any bundle" error message

[vanstee]

When installing and configuring a bundle, you may forget to enable the bundle or assign it to a relay-group. However, if you try to run a command that you haven't correctly configured, you get a confusing error message stating that the command could not be found. We need to improve these error messages so new users can figure out what went wrong without asking in chat.

• When a bundle is installed but disabled. We should explain that the bundle was installed and the command exists but it is currently not able to run because it has not been enabled, and then give them the chat command to enable it @cog bundle enable pagerduty
• When a bundle is installed and enabled but not assigned to a Relay group. We should explain that a bundle cannot run until it is assigned to a relay group that contains a relay, and then provide them the command to fix it @cog relay-group member assign default pagerduty
• When a bundle is installed, enabled, and assigned to a relay-group but still can't run. This typically happens when you've configured everything correctly but you haven't waited for the relay refresh interval to pickup the new bundle. We should explain that and tell them to wait.