Save preference for explore / calendar page

[sebastianlay]

We should somehow determine whether a visitor prefers one view over the other (explore vs. calendar view) and redirect the visitor to the appropriate view when he returns to the site later. Doing this upfront doesn't make sense since the visitor has not seen the two views yet. A better way would probable be to simply remember which of the two views the visitor saw last and redirect to that one. Saving this preference would be most easily done via a cookie. We would then have to check whether some form of cookie banner is necessary or if we can avoid it.