changing append to extend for adding base class attribute code. Also adding real and imag properties to the gauss_param object to reflect that it is a complex number

Added abstract class for mirror and beamSplitter classes, providing all of the shared functionality.

mirror params.

objects that have properties dynamically added to themselves need to declare themselves as new classes, with a base class of the original. Otherwise when we add properties we add them to all instances.

- extending SIfloat to work with lists
- adding SIfloat to axis conversion.

Adding in more parsing for finesse commands. Can no specify a chunk of finesse codee. Various other fixes included too. Currently GUI isn't working.

More changes on how it all works. kat.run() now returns a runkat object which contain all the varios information like timestamps, data, headers, version. Gui now has spaces connecting components up. Also added 'Export to SVG' option which is nice, however the SVG renderer mucks up the gradients on the components