Write style to QGIS

[tomchadwin]

This is easier than getting the style out of the webmap in the first place.

[tomchadwin]

Implemented for Leaflet styles:

• simple style object
• simple style function (return value only)
• switch statement
• if statement

Only working so far with polygons. No expressions, and many assumptions - PoC, but possibly covering quite a large number of common map styles.