Small fixes for JOmnifactory

[nathanwbrei]

This is so I can remove a bunch of TODOs inside eicrecon.

• Does JMultifactory correctly catch std::exception and wrap it in a JException?
• JMultifactory::GetTag,SetTag are not currently usable due to weird prefixing choice
• JMultifactory was missing plugin name and app. Might be already resolved?
• Revisit the question of why we need to pass in japp to JOmnifactoryGenerator