Don't depend on base tag

Don't depend on the html header's <base> tag, which is removed in plonetheme.sunburst 1.5 as part of the Plone 5 PLIP. This makes ``plonetheme.sunburst >= 1.5`` usable together with ``wildcard.foldercontents < 2``.

Plus: some JSLint and PEP8 fixes.