Purge old neutron manifests and move our customized files

outside from community neutron manifest.

This makes it easier to carry rebases forward and prevent conflicts.
This may be squased into the merge from upstream commit.

Authors: Andrew Woodward, Sergey Vasilenko

blueprint: ml2-neutron

Fuel-CI: disable
Change-Id: I9b69c2ab4cb4e476083ec9516f442d9b1911b666