Implement code for basic kicad import

[Freshdouble]

This implements some basic kicad device import function.

The kicad project must assign the part id to each element in the schematic and create the bom. With the bom kicad creates an xml file which contains all the parts on the board and every field from those parts.
The new xml file upload in the "Create device" window accept this xml file and will create a the device with every part in the schematic.

If a part doesn't have a id field, the upload will fail in the current version.

This code is currently experimental and not fully tested with invalid xml files. Only the import of a simple kicad example project was done.

I dont know which branch should contain experimental code so i used the master branch.

[EvansMike]

Works for me, but I commented the
throw new Exception("No ID for part " . $comp["ref"]);
lines so it could skip parts that have no ID field and still successfully create the device, but with missing parts.
Maybe a warning message would be better?