Boms-Away Enhancements

[aaronw2]

I have added a number of enhancements to Boms-Away as I attempt to teach myself Python.

• Boms-Away will now accept the schematic file from the command line to better integrate with KiCad EESchema.
• The supplier URL and a part description are now supported fields which are useful in BOMs
• Two new export filters, one for something close to what PCBWay wants and the other exports Excell XSLT.

I still have a number of features planned.

• Save default to schematic directory
• Sort references in column
• Sort BOM by reference
• Integrate Octopart and Digikey support

[aaronw2]

I have made some more enhancements, however, I have not had much time lately to do more work on it. I also upgraded support to Python 3.