Merge autopilot into bus

[ChrisSchinnerl]

The autopilot API should be merged into the bus. That means

• make autopilot a sub-package of bus
• existing autopilot routes on bus can be removed see #1657
• no more multi-autopilot support which simplifies the database schema see #1657
• bus /scan endpoint should score host if autopilot is enabled

[peterjan]

@ChrisSchinnerl what's the reasoning behind scoring hosts in the scan endpoint if the autopilot is enabled? Do we still want to score a host when we perform checks on hosts in the maintenance loop? Do we want to scan more frequently? The reason I'm asking is the LowScore field which needs calculateMinScore, which we calculate across all hosts. There's many ways around that but before diving in I figured I'd ask for a little more context.

[ChrisSchinnerl]

The idea was that when you manually scan a host via the UI, you immediately get feedback as a user and don't need to wait for the maintenance to run. So we'd still have the regular maintenance but additionally a scan would also perform some checks.

That said I think we can hold off on that part until v2.1 or v3.0. We might not want to continue having a LowScore check anyway which would then simplify adding this.