Implement Scheduler

[kwiesmueller]

gorcon should offer an easy way to schedule recurring or single time events to be enacted on different parts of the gorcon application.
Some examples of this are

• (re)starting the server
• executing rcon commands
• changing settings
• sending data via other services

To implement this, all available functions for this first need to be generally available through one dedicated internal channel. Therefor implementing of this issue highly relies onto #3 and is mostly blocked by it.

Nevertheless the scheduler functionality can already be outlined.
Acceptance Criteria:

• A comprehensible format for defining and storing said schedule
• A dynamic and general way to store, change and handle the stored schedule according to gorcon's overall architecture
  This includes the ability to update the schedule at runtime, access it from several ends (api, etc.) and persist those changes in a reasonable manner.
• Access to the full set of internal API's offering full flexibility in working with gorcon