Feature/get upload library object

Hey John,

Here's some code I had written a while ago and haven't gotten to sending as a pull request until now.  The main purpose is to implement a way to convert the response of `uploadFilesystemPathsRequest` to a GalaxyObject (I was using this to get the id of the uploaded file) as well as implementing `LibrariesClient.showDataset` which works similar to the bioblend version http://bioblend.readthedocs.org/en/latest/api_docs/galaxy/all.html#bioblend.galaxy.libraries.LibraryClient.show_dataset.

I had noticed you mentioned the meaning of `data_type` to the history contents API (https://github.com/jmchilton/blend4j/pull/21) and I was wondering if this also applies to the meaning of `data_type` in the LibraryContents?

Thanks,

Aaron