Add option to limit dates to certain weekdays

[fapdash]

Based on #42

Maybe privacy.limitDay should be named privacy.limitDays?

TODOs

• Rename privacy.limit to privacy.limitHour or something.
• Accept old privacy.limit configuration, but warn about deprecation.
• Don't accept old and new config key in the same config.
• Test new config checks and warnings?
• Update code to also use limitHour and limitWeekdays instead of just changing the external config