PR/nonPR jobs should be generated at the top level into different folders

[mmitche]

Today we usually have the following:

• We generate a folder for a project and a subfolder for a branch, then generate jobs into that branch
• In the netci groovy files we usually have the following pattern:

[true, false].each { isPR -> ...

This is a little inefficient. PR jobs pollute the rolling/main folder, causing additional data to be loaded all the time when most people only want to look at the rolling data.

Instead, the MetaGenerator could generate a PR/nonPR folder, then set up a generator job for both and call each with the appropriate PR/nonPR job parameter.

Configs wishing to do this would be rewritten, just removing the "[true, false].each { isPR ->". By default, we should not generate the folders for this, only opt-in for now using an additional option in the repo list.