Screenshots paths

[chaggeus]

1. screenshot images should be saved with absolute path that is defined in "robot -d " (as right now it working)
2. screeshots images location in log.html should be defined as relative path if we wanna see those in log.html page (right now it is absolute path), here is a screenshot

How to reproduce a problem:

1. start dockerized env and execute tests as instructed
2. screenshots are saved to same location than log.html file (thanks to hack in docker-compose.yml )
   ... log.html looks like this:
   
3. But in log.html code absolute path is used (even relative path should be used)
   <img src="/robot/results/report-images/JavaFXLib-20180828-094617-378.png" width="602.0px">