Upgrade isis-security-shiro to use shiro 1.2.3 (currently using 1.2.1)

On attempting to upgrade our dependency on Shiro to the latest (1.2.2), found that our the unit tests, at least, do not pass.

The reason seems to be that our globally registered IsisPermissionResolver, in shiro.ini is not picked up, and so IsisPermission is not used to interpret the permission strings (Shiro's default WildcardPermission is used instead).

Not clear at this point whether the issue lies with Shiro, or with Isis misconfiguring Shiro (in a way that used to work).