adding in fsig command (not parsing yet). See example test_fsig.py in bin folder. Also made component variable an optional argument for xaxis and x2axis which will break previous scripts. Did this as when setting the parameter to tune, the Param object contains whatever component owns that parameter so no need to pass it twice. Also stops someone passing a parameter not for the component stated.

adding in more support for nodes. Can now access any node using kat.nodes.n1. Added in functions for Node object to set the gauss parameters. Only added gauss for w0 and z so far.