Undo what was done to close issue #78 .

What I didn't realize when that was implemented is that it switched us from a right-handed coordinate system to a left-handed coordinate system. We want to go back to right-handed to make it simpler to export to 3D tools such as oxDNA.

Let's ensure backward compatibility here by bumping the minor version number once this is fixed, checking the version on import from a .sc file, and swapping the x-z coordinates on prior versions.

Related to web interface issue 488.