Boron-10 0.5.1

Just to get this out of the pipeline: a minor update!
New features:

• alignment tools
• Newman diameter of an atom (so that an atom can be drawn as a plain circle to produce a Newman projection)

Fixes:

• MIME types (Thanks to Alexander Ploumistos at https://sourceforge.net/p/molsketch/bugs/19/)
• Catching exceptions thrown by OpenBabel to avoid program crashes

Version 0.6.0 will include a complete make-over of drawing settings.