Sort by group size (Mentioned in #306). Popular groups sortBy -size

Will lazily update over 2h after pushing.
Linkifies Popular Group heading. Depends on #332 for CSS.
Add Script.installsSinceUpdate & show in author panel.
Merge pull request #333 from Zren/installssinceupdate

Add Script.installsSinceUpdate & show in author panel.
Merge pull request #335 from Zren/groupsize

Sort by group size (Mentioned in #306). Popular groups sortBy -size