router: implement RelativeURLPath
* experimental boosting & name resolution
* adding fields to search
* updated schema
Merge pull request #177 from rogpeppe/076-relative-url

router: implement RelativeURLPath

We can use this for generating correct relative URLs in pages that
we serve (we'll use it initially in the generated SVGs for bundles).

Also add some copyright notices that were needed.
Merge pull request #180 from urosj/v4

CS Search: Experimental boosting & name resolution