packer/template: Test that builder.rawConfig excludes name

The name isn't actually part of the builder config, so it should be
removed during parsing.
packer/template: Remove name from builder rawConfig

This prevents the builder from rejecting the name (which it doesn't
know about) when validating the config.
Merge pull request #199 from qur/builder-name

packer: builder name should be removed from rawConfig