Installing tools from ToolShed should (optionally) run their tests

In the IUC tool developers best practice guidelines https://galaxy-iuc-standards.readthedocs.io/en/latest/best_practices/tool_xml.html#tests we stress tools should have tests, and encourage this with things like ``planemo lint`` (and facilitate it with ``planemo test`` etc).

However, right now it appears that when a tool is installed into Galaxy from a Tool Shed, any tests included with the tool are not being run. This should happen (ideally by default, but optionally would be an improvement) with the test results readily viewable (to aid bug reports to the tool authors).