More splitting apart of tree-building from GBM-trees

Can now split individual bins as a function call.
Calling function decides which bins, so e.g. RF & GBM have different
rules here.
R library for H2O
Merge branch 'master' of https://github.com/0xdata/h2o
Cleaned up a few folders
Added build for H2O R library
Delete some R files that don't belong in git.
changed name of an inspect checking util in h2o_cmd.py
test_short.py is for testing part-00000b
Merge branch 'master' of github.com:0xdata/h2o
Minor fix to error checking in summary function
Merge branch 'master' of https://github.com/0xdata/h2o
update
Merge branch 'master' of github.com:0xdata/h2o
Add a GBM flavor to logging
Collapse 3 tree-build loops into one loop.

Speedup about 10% on covtype.  Also move some Histogram specific code
into that class.  Rename 't' to 'node'.  Cleanup reporting some.
Added Makefile for R.
Add a bulk-tree-score pass, remove predictions-per-pass

Drop the prediction pass, making it optional.
Another 10% speedup.
Fix build.sh for R build
Merge branch 'master' of github.com:0xdata/h2o
Added mapperport callback for exit.
add a dict of constant columns to the info gathering routine...use it to prune the x list (along with the other prunes) for test_short.py