Extended tooltip support

URL example:
rest/services/ech/MapServer/ch.bakom.radio-fernsehsender/5/extendedhtmlpopup

So far only one extended tooltip has been migrated. (ch.bakom.radio-fernsehsender)

For now link to extended tooltip has not been added to the regular tooltip.

css are now centralized in a css file dedicated to the extended tooltips in chsdi/static/css/extended.css
This file could be compressed during the buildout process, this should be done in a separate PR.