Allow nesting commands under minion names in master ACL config

[johnccfm]

The current code allows ACL's like:-

client_acl:
  # Allow thatch to execute anything.
  thatch:
    - .*

But it breaks horribly on ACL's like:-

client_acl:
  # Allow fred to use test and pkg, but only on "web*" minions.
  fred:
    - web*:
      - test.*
      - pkg.*

This patch fixes this - perhaps not in the safest or most elegant way, but it seems to work.

[gravyboat]

I'm going to need some secondary opinions on this, @BABILEN, @iggy, concerns over this? It's definitely a problem for backwards compatibility but other than that I like the functionality it adds.

[aboe76]

this should be rebased with this issue statement:
#275

[aboe76]

fixed in:
#301