global: iter_suites overlay use

* Allow iter_suites to more easily be used from overlays.

* Adds deprecation warning to import_module_from_packages and
  import_submodules_from_packages.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
restful: decorators fix

* Fixes issues with decorators being called with both bound and
  unbound methods when used from Flask-Restful method_decorators
  attribute (bound) vs normally applied decorator (via @ on class
  method)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
installation: relax requirements

* Relaxes constraints on some requirements.

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>