1.3.9.0

Changes:
Added Preview player in job submit window
Enhanced variable gui support in job submit and scheduler
Several bugfixes, most importantly bring up alert message when ffastrans replies with invalid JSON to history job api call (instead of just not showing new jobs)

If you have an existing up-to-date webinterface, just replace server.exe
Additionally extract the folders
tools/ffmpeg and tools/vlc
as well as copy and overwrite the file prometheus/prometheus.yml

If you do not have yet tools/prometheus folder in your installation, it is too old and you need to start from scratch