Some DRF2 work, pull a too-strong assert

Assert in H2O.putIfMatch seems too strong, pulled.
integrate w/master on DRF
Merge branch 'master' of github.com:0xdata/h2o
Merge branch 'master' of github.com:0xdata/h2o
Mapping of columns domains.

If enums domains of compatible columns do not match, a mapping is
computed and a new vector transforming values is used.