Rename Frame._vecs ==> Frame.vecs()

Also make closing Appendables more lazy.
Remove some unneeded AppendableVec uses - normal Vecs are easier/faster.
Rename ._vecs[].length ==> .numCols()
Rename ._vecs[0].length() ==> .numRows()
Remove debug print, unwind overlapp work
h2oWrapper.init now loads h2o library and returns H2OClient object
Remove H2O R package from target, leaving only wrapper
Updated DPArseTask not send the shared _nrows array over the wire when launching phase 1 (array is created in local init(), so it is shared node-wide, but it is sent as null initially).

Fixes the bug with new compressed arrays stuff (DParseTask size was changing between resends.
Merge branch 'master' of github.com:0xdata/h2o
Initial GBM/DRF prediction is 1/#classes

Instead of predicting the average class distribution.
Drop the initial tree as well, and just guess 1/#classes for every row.
Merge branch 'master' of github.com:0xdata/h2o
Merge w/master