[C++] Refactor IPC vector "loading" and "unloading" to be based on cleaner visitor pattern

[asfimport]

The logic for obtaining buffers and metaata from each array is currently somewhat self-contained in arrow/ipc/adapter.cc – this is somewhat inflexible. See the interface used in the Java implementation: https://github.com/apache/arrow/blob/master/java/vector/src/main/java/org/apache/arrow/vector/FieldVector.java#L52

This may be better implemented using virtual functions and the visitor pattern, which may yield better user-extensibility in the future

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

_{Note: This issue was originally created as ARROW-338. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #256

[asfimport]

Uwe Korn / @xhochy:
Issue resolved by pull request 256
#256