a little cleanup

- make global variable local
- fix doxygen syntax
- update description of datastructures
cleanup call of sunup() function

- move global vars to parameters
- cleanup includes
- add include guard
cleanup qrb calculation

- change internal representation of station coordinates from
  string to double numbers
- drop usage of global variables and make them local funtion parameters
- cleaunp include files
- add include guard
cleanup clusterinfo()

- drop compiler warnings
- simplify
- cleanup include files
- add include guard
- move datastructures to file scope
- rename 'ptr' variable to 'nr_of_spots'
cleanup clusterinfo()

- split out functions not belonging to the cluster display