A few bug fixes

Hey Guys,
Great work on this plugin.  Definitely a handy addition to our Jenkins setup.  There were a couple of things that we discovered during our initial use of the plugin that are included in this pull request.  These are outlined as follows:

1.  Editing the job config caused upstream triggers to be lost.  I was able to fix this by simply adding the config-trigger block to the main.jelly file
2.  The MasterBuild went into an infinite loop when one of the included jobs was disabled.  This was addressed by removing the disabled jobs before starting build.
3.  Small enhancement to include the "disable" button on the main page.

I hope you are able to take advantage of these adjustments.


Cheers!