[trickle] trickle server/channel

[Chovin]

please test and comment

added [p]trickleset toggle - toggles trickle for server/channel list [p]trickleset channel - manage channels in trickle channel list

tested:

• [ ] 1. [p]trickleset displays channels and yes/no for boolean settings
• [ ] 2. [p]trickleset toggle - toggles trickle for server/channel list
  • [ ] 2.1 defaults to toggling
    • [ ] 2.1.1 if toggle on and no channels set, interactive prompt
  • [ ] 2.2 toggling it off stops trickling for the server
  • [ ] 2.3 toggling to server trickles to every channel
  • [ ] 2.4 toggling to channel trickles to channels set with [p]trickleset channel
• [ ] 3. [p]trickleset channel - lists and manages channel list to trickle to
  • [ ] 3.1 left blank, lists the channels set to trickle to (msg if empty)
  • [ ] 3.2 using with multiple channels in one call works the same as if only 1 was used
  • [ ] 3.3 using channels already in the list will remove them
  • [ ] 3.4 using channels not in the list will add them
  • [ ] 3.6 using channels that have only some members in the list will start interactive prompt
    • [ ] 3.6.1 cancel doesn't change the list
    • [ ] 3.6.2 other choices correctly do 3.3/3.4