add parse_presets() to assemble a presets-dictionary
add doctests
add GenericMainWindow class for common main window properties
preset GUI elements in set_defaults() method
inherit all common stuff from GenericMainWindow, adjust README

* default signal-slot connections
* base path handling for file dialogs
* argument parsing
* presets

README files are updated to reflect the new way of specifying presets
remove "plot3d_" prefix from functions
improve docstrings, add examples for doctest
add options to plot additional stats and raw filament points
rename points3d_object to pts3d