ATS Input Spec Release v1.5.1

Fixes a bug in 1.5.0 where a commit was missed.

ATS Input Spec Release v1.5.0

This initial release is numbered to match the Amanzi and ATS release that it works with (also version 1.5). Future releases will mirror those codebases, and it can be expected that ATS Input Spec releases numbered 1.X.Y will match any Amanzi or ATS release 1.X.Z (e.g. major and minor release numbers must match, but patches do not need to match).

This release marks the start of "official" support for scripting ATS input files.