Add a "hasAllPerms" configuration options

At present, I am stuck on all development on my MacBook (e.g. STRIPES-324), because FOLIO-516 has struck in a way that means I can never retrieve my permissions, even after a successful login.

As a temporary workaround for this, I am going to add support in stripes-core a configuration item, "hasAllPerms", which when true means that all hasPerm checks succeed. This should at least make it possible for me to run the Users app; it remains to be seen whether any of the requests it then makes ever succeed.