* DOC framework for keeping API refs for deprecated classes/funcs
* DOC tagging deprecated for 0.20
* suggestion for LDA/QDA deprecation
* simplify deprecation message for GaussianProcess
* simplify deprecation messages
* fixup avoid import QuadraticDiscriminantAnalysis in qda.QDA (and similar for LDA).
* fixup test alias lda.LDA is instance of LinearDiscriminantAnalysis
waterponey