[SPARK-15956][SQL] When unwrapping ORC avoid pattern matching at runtime

## What changes were proposed in this pull request?

Extend the returning of unwrapper functions from primitive types to all types.

## How was this patch tested?

The patch should pass all unit tests. Reading ORC files with non-primitive types with this change reduced the read time by ~15%.

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The github diff is very noisy. Attaching the screenshots below for improved readability:

![screen shot 2016-06-14 at 5 33 16 pm](https://cloud.githubusercontent.com/assets/1514239/16064580/4d6f7a98-3257-11e6-9172-65e4baff948b.png)

![screen shot 2016-06-14 at 5 33 28 pm](https://cloud.githubusercontent.com/assets/1514239/16064587/5ae6c244-3257-11e6-8460-69eee70de219.png)

Author: Brian Cho <bcho@fb.com>

Closes #13676 from dafrista/improve-orc-master.