templates: clean up, tidy and validation of HTML

* validate HTML through W3C validator
* remove inline CSS styles
* use HTML tidy
* fix indentation

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
less: port all CSS styles to LESS

* create LESS file for each template
* refactor and sanetize LESS
* fix identation
* clean up

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>