Initial cut at PCA, currently only JSON output works
Can now call PCA from the R API using prcomp
Fixed browser output and added proportion of variance
Improve R PCA interface
Need to import an additional water.util library
Merge branch 'master' of https://github.com/0xdata/h2o into pca

Conflicts:
	R/h2o-package/R/Algorithms.R
	R/h2o-package/R/Classes.R
	src/main/java/hex/KMeansModel2.java
	src/main/java/water/api/RequestServer.java
Merge branch 'master' of https://github.com/0xdata/h2o