the bind mount module has been tweaked in a couple ways:
- rename hexchen.* to hacc.*
- rename bindmount to bindMount to make it consistent with usage in
the nixpkgs container module
- add a hacc.bindToPersist option as shorthand for prepending /perist
to a path via bind mount
the nopersist module has been shortened a little by moving
service-specific things which are used once out into the individual
service files, and removing those which we don't need at all (this also
means we get to loose a mkForce or two in case of mismatches between
hexchen's and our current config).
