ShapeFile DataSource prototype

[pomadchin]

This is a draft and example of how the shapefile datasource can be implemented. Its functionality is pretty limited:

• it can only extract geometry out of a SimpleFeature
• it works with a single shapefile as an input only (which is useless)
• It feels like it deservses a separate sub project (due to a geotools dep)

I had a question about a Spark shapefiles support, and decided to craft a quick prototype, which def can't be merged in as is.