Shared infrastructure for varimp computing.
WIP varimp on the fly
Merge remote-tracking branch 'origin/master' into mm_fix_varimp

Conflicts:
	src/main/java/hex/gbm/SharedTreeModelBuilder.java
Merge branch 'master' of github.com:0xdata/h2o into mm_fix_varimp
Make the method CompressedTree#score public.
Variable importance for DRF is computed on the fly.

Now, for each tree its correct votes on oob rows are
tracked on the fly.

After each iteration votes of new tree per variable on shuffled
oob rows are collected. However, this stage is still expensive
and depends on number of OOB rows and features.

Furthermore, commit introduces shared infrastructure for variable
importance computation.

Commit joke for Kevin: Two random variables were talking in a bar. They thought they were
being discrete but everybody heard their chatter continuously.
Merge branch 'master' of github.com:0xdata/h2o into mm_fix_varimp

Conflicts:
	src/main/java/hex/drf/DRF.java
	src/main/java/hex/gbm/DTree.java
	src/main/java/hex/gbm/GBM.java
	src/main/java/hex/gbm/SharedTreeModelBuilder.java
Merge branch 'master' of github.com:0xdata/h2o into mm_fix_varimp

Conflicts:
	src/main/java/hex/drf/DRF.java
	src/main/java/hex/gbm/DTree.java
	src/main/java/hex/gbm/GBM.java
Merge branch 'master' of github.com:0xdata/h2o into mm_fix_varimp

Conflicts:
	src/main/java/hex/drf/DRF.java
	src/main/java/hex/gbm/GBM.java
	src/main/java/hex/gbm/SharedTreeModelBuilder.java
Missing annotation.
I am not a designer, but i like nice things.
Variable importance is now shown in sorted order.
Disable old-school computation of variable importance in DRF.
Merge branch 'master' of github.com:0xdata/h2o into mm_fix_varimp