In netlist generation, changed the rule to calculate netnames of nets with labels:
    Previously, named nets (i.e. nets with local, hierarchical or global labels) have their name
    defined by the first label found in list.
    So net names could be changed without really changing the schematic.
    Now the names are calculated from the rules (by priority order) :
    1 - use the most top level labels in hierarchies.
    2 - use global labels first, local labels next (hidden power pins names are global labels).
    3 - use alphabetic sort (so, if GND and AGND are connected, the net will be always named AGND,
    and adding a VSS connection cannot change the net name)
    So power nets and nets that have more than one label cannot have their netname changed
    if there is no actual change relative to these nets names in schematic