Build-in search rules editor

[sorgoz]

I think we could have search rules editor implemented right in the stable addon's code as an internal page and switcher.

benefits:

• one stable code instead of two branches (no need to merge every time)
• really quick switching between production rules / dev rules

To prevent users from switching rules, this internal page might be safely removed during packaging.

[sorgoz]

won't fix: no time.