PCA bug partially solved
zero tolerance added for whitening in PCA
added unit test for null spectrum approximation in quadratic time mmd and a minor spell correction
Merge pull request #2071 from mazumdarparijat/pca

PCA bug partially solved
Merge pull request #2087 from lambday/develop

added unit test for null spectrum approximation in quadratic time mmd and a minor spell correction
Refactor MulticlassMultipleOutputLabels
Added back the commented code.
Removed old enumerator
Merge pull request #2088 from Jiaolong/refactor_MulticlassMultipleOutputLabels

Remove MulticlassMultipleOutputLabels
Added multilabel reader in LibSVMFile.
Added multilabel writer in LibSVMFile. Updated LibSVMFile unit test.