[Python] Review public pyarrow.* API completeness and update docs

[asfimport]

There are still many names missing from pyarrow.* and ARROW-797. We should do a final review and update before 0.3

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

Related issues:

• Arrow 0.3 release (blocks)

_{Note: This issue was originally created as ARROW-818. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #557

[asfimport]

Uwe Korn / @xhochy:
Issue resolved by pull request 557
#557