Add Defautl date option like `one month(or week) before` in Date Filter

[superjcd]

As you see if I want to pick a default value for a Date filter, I have to select a fixed date。

The downside is the default date I set before will no longger be a proper suggestion for users as time goes on
, so how about giving user an option like "one month(or week) before"?

[Luiggi]

if you pick a filter with a relative date it'll let you use that as default values