Add formatting option for table columns

#### Is your feature request related to a problem? Please describe

Current table supports displaying data "as is" and transforms some types of data as it sees fit - e.g. dates are turned into localeString with time. We could add more flexibility to this by introducing [formatting options](https://wave.h2o.ai/docs/expressions/) to further separate data from their presentation. The new attribute can be called `cell_format` and be added to existing `table_column`.

Start by locating the existing table_column entry point and reviewing the linked formatting options documentation. Determine which formats the new cell_format attribute should accept and how formatted table values should be displayed; done means the option works without changing existing table behavior.

Written by the indexing model from the issue text.