1. After importing a structure, the sticks were not selected: fixed

 
2. Small cleanups of the code

3. New feature: The sticks can be represented as entire cylinders. One can 
choose either single cylinders, which are parented to an empty, or one single
mesh object including all sticks. 
This feature is quite suitable for structures, which count more than 1000 
sticks. When the sticks are represented by one single mesh object the
handling in the 3D scene is much faster.
Note that the layout of the preferences in the file dialog had to be also 
changed since there are more options for sticks now.
 
Blendphys.