added checkidcount to vertexfactory that is called when a vertex is parsed to avoid two vertices having the same id
undone passing the reference of the mainwindow as an argument and created static getter in vigralGUI instead
renamed static getter of vigralGUI instance from getMainWindow to getInstance and made VigralGUI a singleton
refactoring: deleted white space
cleared picked vertices on changing mode in vigral gui
sorted the values in combobox of requirementdialog
added comments