Remove protocol type aliases from sbt.client

 * in some cases (specifying a type parameter for example) these
   don't seem to be interchangeable with the original type
 * having two paths to the same type name is confusing for
   API users
 * we only had a haphazard subset of sbt.protocol aliased into
   sbt.client anyway
 * DRY
Merge pull request #203 from sbt/wip/havocp-remove-client-aliases

Remove protocol type aliases from sbt.client