Let users search by things other than name

[amoeba]

Harli mentioned wanting to be able to filter characters by level. I think it'd be easy enough to handle a special syntax like field:value (e.g., level:275) in the general search box.

[amoeba]

First version of this is in and it works okay. It doesn't support ranges for numeric fields like level, so you can't do level>200 or something, which'd be cool.

[amoeba]

@jkisor wrote up an alternative implementation that does things a bit different at 5b24feb. I'll plan to have a look when/if I revisit search in the future.