fixed not working subgroup choosing. included up and down keys to choose
added key up-down-arrow support for grouplist
added automatic selection of first element in subgroup list
removed trivial group c1, ensured subgroup order to begin with the group itself
removed typos in statusbar, used full notation where possible
inserted code for showing 4d symmetries. somehow this does not work ... he cant find the resources. commented out for now
renaming of introduction and adding section Mathematische Grundlagen
wrote something about projektorganisation, added todo for annotations, changed fu-logo to pdf version
Merge branch 'master' of https://github.com/Ryugoron/point-groups
some scribbles for math prerequisities
add introduction, minor fixes, citations
Merge branch 'master' into Generatoren