C++: Represent boolean array data in bit-packed form

[asfimport]

This is not explicit in the Arrow specification (we should make this concrete), but has the additional benefit of making code for null bitmaps and boolean arrays interchangeable.

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

_{Note: This issue was originally created as ARROW-37. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
#40

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 40
#40