Twitter search channels 2: it's back for revenge

The review in #12 was a failure. I'd blame you ghosts but I was also somewhat in a hurry to get it merged.

It landed in develop, it was about to get submitted to master but didn't. I just reverted it in 8e68ec107bd9651bbea4af58b4eedb3d23922ae4, mostly because it was becoming annoying to do twitter patches around it.

As I said in that commit:

>It never landed in master because it 'leaks' contacts, as in they never get removed from the channel/blist until the account gets removed, which becomes a big issue with high activity hashtags.
>
>Sending it back to review, will apply again once it's fixed.

So, known issues for now:

 - [ ] Contacts leak
 - [ ] The limitation to hashtags is silly
 - [ ] Whitespess

I don't even know what else, tbh. Quoting a @ghost reviewer:

```
17:41 <ghost> it needs a lot of work
17:41 <ghost> waaaaay too "hacked" together
```