introduced use of copy module

Signed-off-by: LK <LK@uni>
added ToDo list: /doc/todo.txt

Signed-off-by: LK <LK@uni>
moved UTM<->LatLon to conversions.py

Signed-off-by: LK <LK@uni>
extended file structure - modules for all steps existing - still partly empty though

Signed-off-by: LK <LK@uni>
moved old ptplot.py to legacy folder - inserted new plotpt.py instead

Signed-off-by: LK <LK@uni>
added imaging/mohrcircle module

Signed-off-by: LK <LK@uni>