Global check for OS
At some points througout the hole VISPA code the OS needs to be
determined. This can be done in Python by various ways, e.g:
platform.system(), sys.platform, …
It should be noted that checking these variables with if-statements, it
can lead to a wrong detected OS and therefore to a wrong behavoir.
Proposal:
Provide a global class to check the OS. All supported systems should be
detectable.
(from redmine: issue id 942, created on 2012-04-21)