Ability to fill missing values

[exalate-issue-sync[bot]]

The ability to specify a fill value to use for missing values. This could be a constant string for non-numerics, a constant number, or MeanImputation.

[DinukaH2O]

JIRA Issue Migration Info

Jira Issue: PUBDEV-2378 Assignee: New H2O Bugs Reporter: Robert Coop State: Open Fix Version: N/A Attachments: N/A Development PRs: N/A

[maurever]

Available for GLM and GAM. Inspect if it is possible to implement for other algos. See https://docs.h2o.ai/h2o/latest-stable/h2o-docs/data-science/algo-params/plug_values.html