Wrap the table type with helpers and add FromTable trait.

[acmcarther]

Its pretty clunky to work with tables, especially compared to the nice coercion other types have. it would be nice if we could hide some of the cruft behind a real type.

Additionally, a small udp lib I'm working on started using a trait FromTable to automate conversion between a table and the desired type. It should be formalized and included in the base library.