Update GitHub event handler and change filter
Update GitHub event handler and change filter

* load all URL variants from GitHub payloads to allow
  a Repo() config to use any of them

* update PR change filter for layers to use a function
  that matches the target branch against the branches
  configured for the Layer() object.

Signed-off-by: Matt Madison <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@madison.systems>

madisongh/autobuilder