Jump to previous/next line involving current user

Created by: trepidacious

Something like up/down arrows to the left of my user icon, at the bottom of the channel window. Clicking up would scroll to the previous line involving me - either something I've said, or something @ myself. Repeated clicking would go upwards. Bonus points for skipping contiguous blocks of lines involving me. Clicking down would go to the next line involving me.

This would be similar to the current system for scrolling back to "fresh" mentions of the current user, but would always be available.

A more general implementation would be an improved in-channel search with a search term box, where the up/down arrows would skip to the previous/next found search term, with some syntax for looking for lines involving current user. For example involving:user, where user could be me to search for current user, plus say from:user, to:user and @user (to and @ could be synonyms). involving:me would be then be the default search term.

Motivation: I often come back to a channel after being afk for a while to find that the conversation I was having with someone has ended up a good way back in history. They might not have said anything new @ me, so there is no mention to scroll to. For example I might want to review what someone said to me the day before, perhaps in order to carry on the conversation. Currently search is not really any use for this since it is not in chronological order, but even if it could be used for this it would be much easier just to have the buttons as described. Most users will presumably be most interested in parts of the history where they were talking, so this seems like a useful way to skim back and forth through history.

from:user is already implemented in search.

A lot of suggestions mentioned here about search already have their own issues, https://github.com/gitterHQ/gitter/milestone/11