EnvSim documentation/ cleanup

[jokaICS]

The WP3 EnvSim tools (libenvsim, SimCtrl, TrackViewer) should see some final housekeeping at the start of 2016:

• [ ] clean-up libenvsim (remove outdated/ deactivated code; remove any left-over hacks; update code comments)
• [ ] Provide some basic getting started guide for using SimCtrl with the WP3 standalone distribution
• [ ] Provide introductory guide on the EnvSim principles/ architecture
• [ ] Provide a basic tutorial on track scripts (TrackViewer)