Add commands to jump to next message matching query

[arekfu]

Hi,

This pull requests adds a jump command to thread mode to move to the next/previous message matching a specific query. I have added the following default bindings in thread mode:

/ = prompt 'jump '
n = jump
N = jump --backwards

This is intentionally similar to vim's behaviour, but I had to change the binding for editnew to 'ctrl n'.

Perhaps it might be useful to add default bindings for jump tag:unread and jump --backwards tag:unread.

Eventually I would like to add a similar feature to search buffers, but that needs a bit more work because search buffers do not have the convenient focus_next_matching and focus_prev_matching methods.

[arekfu]

Oops, probably the last commit wasn't such a great idea. ? is reserved for the help screen.

[pazz]

Hi!
I like the move next matching .. commands and would actually prefer only those and no hardcoded
aliases jump. Since most of us use keybindings anyway i think those are totally sufficient.
How about you send a new PR containing the move-patch, one that cleans up the
help move accordingly and maybe one that introduces some default bindings? thanks!

[pazz]

I believe that this functionality is now provided by the move next QUERY thread command.