Choice palette for join and aggregator select

[anjakefala]

The following was shared by @saulpw as a comment on this issue. I wanted more people to see it as a discussion post. =)

@saulpw's text starts here:

Okay, so I repurposed the command palette for chooseAggregator and chooseJointype. There are only a couple of remaining uses of chooseOne but they are fairly minor (theme chooser, signal chooser for the procmgr, ibis sidebar chooser). The palette has been improved/changed in a couple of subtle ways, too:

• if there aren't enough matches, the palette is filled out with your "favorite" commands, as measured by how much you've used them this session (could be saved in the future);
• you can select multiple aggregators and they append to the list (and are removed from the palette list)
• input-specific help is shown in the sidebar if disp_help == 1
• the intra-string match highlight color is now options.color_match (red in the default theme)

With quick-select on the 0-9 number keys, you currently can't type options with numbers in them, e.g. the q3 aggregator. Also the individual percentile aggregators (e.g. p10) are removed from the aggregator choices; now you can only choose their whole quartile group (e.g. q10).

This and a few cosmetic issues aside, I believe this palette mechanism should be sufficient to replace the fancy chooser, so I'm going to close this issue for now. Please let me know how you like this new choosing mechanism, and open new issues for anything that needs to be changed.