Add HTML class to tool select elements corresponding to data parameters.

This will allow targetted enhancing of them via JavaScript.
Allow running tools on multiple datasets simulatenously.

Like with workflows, but with tools. Only works with a single input so far - just need to follow the pattern of this (https://bitbucket.org/galaxy/galaxy-central/commits/26f7825cc871c752d1e79bbe8984857d67f1eb0e)  changeset to make it work with multiple inputs.