Experimental support for Tachyon FS

Changes:
 - added tachyon 0.4.1
 - Persist layer for tachyon
 - url for tachyon is tachyon://<address of server/<filename> - e.g.,
   tachyon://localhost:19998/covtype/covtype.data
Removed transient dependencies for tachyon.
Minor parser helper.
Tachyon libraries
Increased limit of predictors in GLM2 to 10k from 5k
Merge branch 'master' into tomas_glm
GLM2 update: fix of validation with lambda_search and strong_rules on. GLM2 now passes in set of active columns (to avoid running xval models on full set or again the whole regularization path) to the n-fold models. Active columns should be largely compatible.
Merge branch 'tomas_glm' of github.com:0xdata/h2o into tomas_glm
Experimental support for Tachyon FS

Changes:
 - added tachyon 0.4.1
 - Persist layer for tachyon
 - url for tachyon is tachyon://<address of server/<filename> - e.g.,
   tachyon://localhost:19998/covtype/covtype.data
Removed transient dependencies for tachyon.
Minor parser helper.
Tachyon libraries
Mimic Tomas fix for platform vectors.
Fix of missing byte skip during loading
value for chunk.
Fix NPE in Parser if parsing multifile set with empty file.
GLM2 update: lambda_search only keeps (and cross-validates) "significant lambdas". Lambda is (for now) considered significant if it improves deviance explained (on the training data) by at least 1%.
Work towards PUB-603.  Layer indexing is still out-of-whack.  Back-prop needs to only work on TanhPrime layer, which shares the matrix with the Tanh layer, but uses the transpose.  Layer stats currently fails and leads to early termination of the run.
GLM2 update: AUC thresholds can now be changed (preparation for having proper AUC computed by collecting meaningful thresholds in special task executed after glm (sub)model is done.
Fix indexing.
PUB-603: Fix memory leak.
TODO: override scoreImpl to do reconstruction of Frame based on auto-encoding network.