Added a Glacier plugin that computes the sha256 tree hash checksum.

This plugin will also compute the sha256 checksum required for
sigv4.  This eliminates the need to read the source file two
times locally to compute both checksums.
Reworked Api Translation and how service plugins/customizations are applied.

The Api::Translator now checks for the configured plugins instead of
the apis rake task.  This allows plugins to be applied at runtime.
Additionally, you can define a service translator to modify the
Api for specific services.

Currently a new service translator has been added for the Glacier
API that converts timestamps from strings to actual timestap shapes.
Additionally, the checksum param is removed here instead of
at runtime.
Regenerated all APIs to have a trailing new-line.