LDPatternCreator - Major Security Release 1.5.7

[Philippe Hurbain]

I let Nils provide more detailed explanations if needed, but in the meantime...
- Fast triangulation: there is a feature enable in edit menu, here Fast triangulation and Fast triangulation II are both checked.
- Mirroring occur - AFAIK - centered on center of mass of selection, giving weird decimals and so on. Because of this I almost never use this feature, but instead use "mirror with merge". Important: while simple mirror does mirror selection, mirror with merge first duplicate selection then mirrors the duplicate. If you copy/paste first, you get overlaps...