Set summer mode feature

[seppeel]

I would like to completely turn off my thermostats via script. on a german fritzbox you have to add a "Heizung aus" period. because multiple periods can be added its probably useful to be able to list and delete these periods too. this is the last step to completely automate everything regarding my home temperature :-)
thanks for your work.

[bpicode]

Managing these periods is not part of the official API [1]. It might be possible to support it nevertheless, I'll keep the ticket open for the time being.

[1] https://avm.de/fileadmin/user_upload/Global/Service/Schnittstellen/AHA-HTTP-Interface.pdf