cosmetic changes to liftables

Namely:
1) Moved definitions of Liftable and Unliftable into a separate file.
2) Inlined internal names that were only used in StandardLiftables.
Merge pull request #3279 from xeno-by/topic/cosmetics

cosmetic changes to liftables
SI-8035 Deprecate automatic () insertion in argument lists

This promotes the () insertion warning from -Ywarn-adapted-args to a
deprecation warning. -Xfuture tunrs it into a compiler error.

Auto tupling remains unchanged for now.

The tests have been fixed the following way:
- Warnings caused by general sloppiness (Try(), Future(), ...) have been
  fixed.
- Warnings which raise interesting questions (x == (), ...) received an
  updated checkfile for now.