Parameter 'lineOffset': offset line to the left or right.

[plepe]

This parameter offsets a line to the left or the right.

[plepe]

After I pushed the pull request, I noticed that there's already a similar pull request: #57.

Pull request #57 solves this problem quite differently, it will first offset the line and then calculate the position, whereas my pull request calculates the positions and then offsets the symbols. You can notice the difference with these screenshots:

With lineOffset -15 (blue) resp. 15 (red):

With symbolOffset -15 (blue) resp. 15 (red):

I think both variants are interesting. I would exchange the parameter names though, because in my pull request the symbols are offset (so symbolOffset would make sense) and in #57 the lines are offset (lineOffset). What do you think?