In 3-step booking, choice of days is not limited

[pferreir]

When using the 3-step booking process, one can successfully pick any future day for a reservation, regardless of the "maximum days in advance" setting.
The result is a (super ugly) error message containing an error report.

One solution would be to show the "bars" of rooms that are not "bookable" for a specific day already in red (or another explanatory color) in the availability view (with an informative tooltip).

[jdafflon]

Fix: ​https://github.com/jacquesd/indico/commit/738fcdf8376e7267b6e58585060d15ea026f2dac
Post fix changes: ​https://github.com/jacquesd/indico/commit/908ecdb50ca9deace1449ab55436af303db6b8f3

[jmonnich]

Rebased branch: ​https://github.com/jacquesd/indico/commits/1586-fix-booking-days-limit