new combo box for attr calc type
cleanup, added some comments
attr calc: vectors now selected via combobox
fixed predefined types and disabled types in attr calcs
fixed typo varaible :-P
fixed table column spacing attr calc
attr calc: improved code, variable table not editable anymore
attr calc: variable name now editable again
cleanup
attr calc: new tree view generation, improved adding variables
attr calc: deleting variables by renaming to empty string