Move YEAR definition to version.py

If it needs to be hardcoded (for the sake of reproducible builds),
it should be together with the other hardcoded version info.

And yeah, two months in, let's move to 2019.

version.py

@@ -4,3 +4,4 @@ major = 3
 minor = 1
 status = "beta"
 module_config = ""
+year = 2019