Allow more control over automatic reboots

[TechD123]

Scenario: User has install updates only while charging and automatic reboots when idle enabled to benefit from rapid fixes to security vulnerabilities while still enjoying maximum device usability.

However, this can lead to inconveniences such as missed phone calls and times of unavailability in critical moments, as for example mentioned in #91 (this issue is different because it focuses on the actual installation, not the application of the update through a reboot).

I have two suggestions that I haven't seen proposed in this issue tracker or the main one yet.

1. I suggest exposing an additional setting when automatic reboots when idle is enabled, so the user can specify "Only apply updates if my device has been idle for x hours".
2. Independently of this, when automatic reboots when idle is enabled, I suggest exposing an option for the user to specify a time frame in which updates are never to be applied by rebooting (e.g. regular work hours).

I feel like the latter would be more helpful since determining the idle state is somewhat broken depending on usage.

Thanks for your efforts!