Refactoring `Edge` into a class, stage 1.
Module `Edge` has been converted into a class.
This will allow creating many instances and storing their own commands with them, instead of separately.
Which has been module methods, now they are instance methods which manipulate the instance data.
Two additional methods, `startPoint` and `endPoint`, can obtain the coordinates of the beginning and end of an edge.
Main source file has been updated to use this new class.
A new class `Symbol` has been added.
It will be used to read a library symbol from the XFL file and parse its data (edges, fills etc.).
The code for loading edges and managing them will be factored out into this class soon.
Refactoring `Edge` into a class, stage 2.
Now edges are stored in `Symbol` instances as `Edge` objects, which simplified the main source file a lot.
Refactoring `Edge` into a class, stage 3 (final).
`Symbol` class moved to a separate source file for better clarity.