Design-django-theme

- Bootstrap Italia v2.3.6
- Removed unused depenendences (thanks to mdavino)

- Aggiunti attributi per l'apertura dell'overlay del menù (Fixes italia/design-django-theme16) (https://github.com/italia/design-django-theme/pull/17/commits/81e27458706705ff6c1dd51431ea1a3a160393f0)

Grazie gpantanetti

Fix Bootstrap Italia version in CDN URL

Avoid CDN to load sprites.svg, this causes "Unsafe attempt to load URL" error.

- Moved bootstrap-italia.bundle.min.js in footer;
- Select input CSS class fixed in widgets/select.html

Thanks to [mluigi](https://github.com/mluigi)