Post upgrade to 2.0: Consider re-adding support for features that were removed in the upgrade

[koernerfelicia]

1. stopovers (see here)
2. reference resolution (see traces here or here)
3. city correction (see traces here or here)

It's not clear whether these worked in 1.x. There is little information about 2, and 3, but we can see from nlu and domain that there were some attempts to do this.