Populate Data Explorer params with URL params

[Lhc_fl (Linca)]

This PR should be able to make up for it:

https://github.com/discourse/discourse-data-explorer/pull/298

@Nacho_Caballero

Something like:

mysite.com/g/my-group/reports/6&params=%7B"months_ago"%3A"3"%7D

Its effect is as shown in the above quote