Document ENUM as a logical type

[asfimport]

ENUM is used to annotate enum type in Thrift, Avro, and ProtoBuf, but it's not documented anywhere in parquet-format.

According to current (1.8-SNAPSHOT) code base, ENUM is only used to annotate BINARY. For data models which lack a native enum type, BINARY (ENUM) should be interpreted as a UTF-8 string.

Reporter: Cheng Lian / @liancheng
Assignee: Jakub Kukul / @jkukul

PRs and other links:

• PR #54

_{Note: This issue was originally created as PARQUET-322. Please see the migration documentation for further details.}

[asfimport]

Ryan Blue / @rdblue:
@jaltekruse, I'm assigning this to you since you brought it up on the dev list. Good to know that there is already an issue open to track it.

[asfimport]

Ryan Blue / @rdblue:
Merged PR #54. Thank you for contributing the fix, @jkukul!