stop PLC before unloading


This fixes segmentation fault if service was quit without stopping it.
It has happened if Beremiz service was quit using taskbar icon or by
closing Beremiz IDE (in case of autostarted local service).

In second case to trigger the bug following step has to be done:
1. Open Beremiz IDE
2. Open project, compile and connect to LOCAL:// runtime
3. Transfer and start the PLC program
4. Open other project without disconneting the PLC runtime
5. Close Beremiz IDE

This project contains wamp client config to be loaded at runtime startup.  

project_files/wampconf.json

wampconf.json is in "Project Files", so it is copied to runtime's working directory, and then loaded after program transfer + runtime restart.

Otherwise, wamp config file path can be forced :
./Beremiz_service.py -c  /path/to/my/wampconf.json /working/dir

Crossbar test router configuration is available in .crossbar directory. Start with :
crossbar -d start