Adding support for support on 'project_name = *' to support querying all projects

[zhujian0805]

Can we add the support for the 'wildcard' on 'project_name' in the config file, so we can use it as 'allTenant' to list all resources in all tenant?

the reason is because i have around 20 regions, and 60 projects in each region, if i go the configuration path, i would need too man connections, could you add that feature?

this also should apply to other openstack resources as well.

appreciate!