[Therion] merge lines in xtherion

[MD]

> On 26. Jul 2019, at 10:37, Benedikt Hallinger <beni at hallinger.org> wrote:
> 
> What exactly is the problem with two separate lines in this case?
> Just curious

For example my TopoDroid exports tend to have half a dozen separate lines, where One would be enough. Changing styles etc is a pain this way.

Also „convert to curve“ gets better results with a single line.

—max