arrow

ARROW-889: [Python/C++] Unify PrettyPrints between Python and C++

My main intention was only to have `PrettyPrint` for `ChunkedArray` instance but as the Python and C++ output was quite diverging, I have attempted to unify both. During that I came across many untested and unimplemented edge cases that I also fixed. Thus this turned out slightly larger than expected.

Author: Korn, Uwe <Uwe.Korn@blue-yonder.com>

Closes #2278 from xhochy/ARROW-889 and squashes the following commits:

002d7b04 <Korn, Uwe> Make test_string_format Python 2 compatible
f9ce993c <Korn, Uwe> ARROW-889:  Unify PrettyPrints between Python and C++