Support syntax differences between sources, in aggregate image browsing.

[Lurkily]

Some sources have slightly different syntaxes for search. When browsing, I'm not sure I see a way to aggregate multiple sources that use a different syntax.

For example, if one source uses sort: and another source uses order:, using one of these will disrupt results from the other.

It would nice to be able to open up the site options and specify that a search on one tag equates to something else here. For example, sort:random presents that source with a search for order:random instead.