[Format] Add additional language to Schema.fbs to clarify naive vs. localized Timestamp values

[asfimport]

This line https://github.com/apache/arrow/blob/master/format/Schema.fbs#L116 has the potential to be misleading.

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-1020. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #731

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 731
#731