Added component field and refactored static fields to global.jelly

Hi

This is my first pull request so let me know if I've gone about it wrong

I wanted to integrate jUnit output ito Jira but I also wanted to attach the bugs to a component in a project. 
This fails with an exception if the component doesn't exist (like it does if the project isn't valid) but will ignore a blank component

I also refactored the server and user to a global config page as this is the approach the Jira/Jenkins plugin takes. 

I think it will fail the tests as it stands

Please let me know if there is anything I can do to package my change better

Regards
Jeremy