Add Hypothesis tests

[cleder]

Test that the objects can be recreated using .to_string() / .from_string() with all verbosity levels, and repr() / eval() roundtrip.

• [x] geometry
• [x] atom
• [x] containers
• [x] data
• [x] features
• [x] gx
• [x] kml
• [x] links
• [x] overlays
• [x] styles
• [x] times
• [x] views