[Amadeus] Migrate part of Draw cog to Graphs submodule

[czechbol]

We need to migrate the part of Draw cog from Amadeus to Math (as Graphs submodule). Namely the digraph and plot commands.
Please note that the plot command is not behaving exactly as it should but it is very difficult to make it better. Perhaps if you can find an API to get the plots from this could be greatly improved.

See the cog here.

The cog doesn't use a database and is using the so this will be fairly a easy port.

Feel free to rewrite any part of the cog to make it better/more readable