All of `sbtVersion`, `defScalaVersion` and `buildScalaVersions` were
not used anymore. According to @harrah they are coming from really
old days of sbt and are not needed because of changes to how sbt
interacts with different Scala versions.
Similar to task macros, the parsed value is accessed by calling `parsed`
on a Parser[T], Initialize[Parser[T]], or Initialize[State => Parser[T]].
Values of tasks and settings may be accessed as usual via `value`.
1. KList[M[_]] now instead of KList[HL <: HList, M[_]]
a. head, tail work properly in this variant
b. disadvantage is that full type not easily transformed to new type constructor
2. AList abstracts on K[L[x]], a higher order type constructor.
A. Instances written for:
a. KList
b. Seq[M[T]] for a fixed T
c. TupleN
d. single values
e. operate on one type constructor when nested
B. Main disadvantage is type inference. It just doesn't happen for K[L[x]].
This is mitigated by AList being used internally and rarely needing to construct a K.