Removing hudson.matrix classes and associated resources as a first pass.
Comment, but not critical for separation.
isMatrixProject appears unused, but keep for compatibility.
XStream initializations moved to MatrixProject.
Removing MatrixChildAction dependency.
Unclear status of MatrixConfiguration when enableFingerprintsInDependencyGraph mode selected.
Extracting MatrixAggregatable dependency.
DetachedPlugin entry.
Extracting some miscellaneous usages from core/src.
Test harness must depend on matrix-project.
Preparing to include transitional release.
matrix-project 1.0-beta-1
isMatrixProject ought to handle nulls, just in case.
Merge branch 'extract-matrix-project'
Noting merge of #1187.