Merge pull request #1 from zalando/data_model

Data model, design considerations
Merge pull request #2 from zalando/data_model

Documentation
Add experimental stuff on top of worker_spi to run the worker process from another background worker launcher process.
Merge pull request #3 from zalando/data_model

Data model: comments, domains, hardening
add code to demonstrate using shared memory for passing error statuses from workers to the launcher.
Merge branch 'master' of https://github.com/zalando/elephant-worker
Merge pull request #4 from zalando/data_model

Added documentation to functions and column names.
Made sure that the run_job function also does
some bookkeeping in the member_job view, updating timestamp and counts.
Writing casts for text::schedule_matcher
.

I don't like the name schedule_matcher, it should probably be called schedule.
Merge branch 'data_model' of github.com:zalando/elephant-worker into data_model