Update querystring format so param ordering doesn't matter

[avaleske]

Blocked by question to Sean.

Right now, the filtering querystring is brittle. The backend breaks if we pass urls like /listings?filter[$comparison]=>&filter[depositMin]=500&filter[$comparison]=<>&filter[name]=Coliseum&filter[$comparison]=<&filter[depositMin]=900 because fields with the same name get grouped into an array, so the resulting filter object is

{$comparison: ['>', '<>', '<'], depositMin: ['500', '900'], name: 'Coliseum'}

which will not be iterated over the same way the comparisons were specified.

Additionally, if the $comparison param is not specified first, addFilter() breaks entirely.

Sean mentions here that they're open to changing the query string format, and adds some ideas on how we might do that.

Ideally, it's to something that let's us pair a field with a comparison type directly, instead trying to do so by keeping params in a certain order.

[willrlin]

@seanmalbert said there was some work being done to clean up filtering; I think it's possible that fixes this issue as well.

[willrlin]

I think this is fixed now by the upstream merge. @avaleske, reopen if not.