Reorganizing Dockerfile and fixing start scripts

[devnagui]

The patch as promised and the statement required to publish it: I accept OCA for this patch

Let me know if you are interested in publishing the Release Candidates versions too, basically we just need to change the URL where opengrok is downloaded(Second line of the dockerfile).

[tarzanek]

merging, thank you I am wondering if we can somehow get to use universal ctags ...