DRAFT: Load javascript last

[bkmgit]

The aim is to give a better user experience on slow connections, in particular mobile. Some reference material:

• https://developers.google.com/speed/docs/insights/mobile?csw=1#PutStylesBeforeScripts
• https://stackoverflow.com/questions/1860482/when-do-you-choose-to-load-your-javascript-at-the-bottom-of-the-page-instead-of
• https://webmasters.stackexchange.com/questions/883/does-putting-javascript-at-the-bottom-defeat-the-purpose-of-document-ready

If this would be considered, other options are:

• to only have the jquery, title bar loader and footer loader scripts at the top, and everything else at the bottom.
• to add attributes such as defer, see https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script

[lminiero]

Please rebase it on #3302, which moved demos to a different folder.