misc improvements for library usage:

- app: allow custom serviceworker path, or disable altogether
- page download options: add warc/1.0 option
- ui: remove unused small style from chooser
ui: tweak initial refresh time to half second

bump to 1.5.1

src/coll-index.js

@@ -117,7 +117,7 @@ class CollIndex extends LitElement
 
     } catch (e) {
       // likely no sw registered yet, or waiting for new sw to register, retry again
-      setTimeout(() => this.loadColls(), 5000);
+      setTimeout(() => this.loadColls(), 500);
     }
   }