Line now uses new style methods - not ready to merge yet

Hi all,

This one was pretty straight forward, no problems. It did highlight for me the value of getting instance variables for styles since I changed a bunch of instance variable calls to method calls which look up style (I'll point that out in-line).

I also removed the `gui_opts` because it doesn't look like we're using those. I'll point that out in-line too.
In these four calls, setting x2 **and** y2 makes a double call to `enclosing_box_of_line`. That is probably a good sign that I should do something differently . . . but I'm not sure what.