Improve search of parents / elevation - some correction + new options
- improve search of parents
- improve elevation
- correct roof:height when given by osm
- correct tag roof:color > roof:colour to follow osm syntax
- add some tags to force specific and default textures
- add KEEP_BUILDING option in order to select a small number of building to write
- add roof pyramidal
- add handling roof:orientation=accross,along for gabled roof