Initial implementation of NestList.
Initial implementation of FixedPointList.

Also made a tiny adjustment to FixedPoint so that FixedPoint[...] is
exactly the same as Last[FixedPointList[...]], in order to align with
the behavior of Mathematica's FixedPointList, which returns both of the
last two elements even though they are equivalent by the == operator.
Merge branch 'master' of https://github.com/poeschko/Mathics into NestList+FixedPointList
Minor code improvement and documentation edit.
Minor documentation edit.
Merge pull request #112 from freshwater/NestList+FixedPointList

Add NestList and FixedPointList