[C++] Add date/time support to JSON reader/writer for integration testing

[asfimport]

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

Related issues:

• Add integration tests for date and time types (blocks)

_{Note: This issue was originally created as ARROW-620. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #446

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 446
#446