Add support for BOUML

[jefcolbi]

Hi, i like your project.
Sparx EA is great but for small company or freelancer the price is not affordable.
I think it would be great if pyMDG supports open source modeling software. BOUML is really great https://www.bouml.fr/
I checked the code and i see in parser, you already left a place to add custom parser.
Thanks

[Semprini]

Looks like a good feature, BOUML has a XMI generator which won't take a lot to parse. The Sparx XMI parser is very customised to Sparx EA but it's a start. None of my clients are using BOUML at the moment so I have a few other features to add first.