Summary
- merged
- revert most parts of 0e79fa88cab6: somewhat ambitious attempt to move towards "editing" builds via added/canceled workers; retain notion of next_jobs.limit and finished() from 0e79fa88cab6; clarified Job vs. optional Build_Job;
- database performance tuning: prefer light-weight IPC over heavy-duty transactions, following bf377e10ff3b;
- tuned;
- tuned whitespace;
- proper system option, instead of hardwired default;
- tuned signature: fewer warnings in IntelliJ IDEA;
- tuned comments;
- clarified build schedule host: proper module;
- remove unused dummy;
- tuned;
- use timeout as default build time predictor if no data is available;