Rename 'experimental features' to 'feature previews' The idea behind this is that we have a set of feature previews rather than one cryptic experimental flag. A feature preview collects a set of related functionality (e.g. everything related to gradle metadata) that changes existing behavior and thus could potentially break existing builds. The preview options will be removed with the next major release (currently 5.0) and the new behaviour will then become the default.
Signed-off-by: Jendrik Johannes <email@example.com>