Abort a play at the start when no hosts matches, or no hosts are remaining

This change makes a distinction between no_hosts_matched and no_hosts_remaining.

In both cases we do not start facts-gathering, or run any tasks.

In the case that there are no more hosts remaining, we abort running tasks and abort the playbook.

I also cleaned up the leftovers from the previous patchsets, as these are no longer required.

This closes #1187.

Example playbook:

```yaml
---
- hosts: emptygroup
  tasks:
  - action: command date
  - action: command false

- hosts: all
  gather_facts: False
  tasks:
  - action: command ls
  - action: command false
  - action: command true

- hosts: all
  tasks:
  - action: command true
  - action: command false

- hosts: all
  tasks:
  - action: command pwd
```

lib/ansible/callbacks.py

@@ -414,6 +414,14 @@ class PlaybookCallbacks(object):
     def on_notify(self, host, handler):
         call_callback_module('playbook_on_notify', host, handler)
 
+    def on_no_hosts_matched(self):
+        print stringc("no hosts matched", 'red')
+        call_callback_module('playbook_on_no_hosts_matched')
+
+    def on_no_hosts_remaining(self):
+        print stringc("\nFATAL: all hosts have already failed -- aborting", 'red')
+        call_callback_module('playbook_on_no_hosts_remaining')
+
     def on_task_start(self, name, is_conditional):
         msg = "TASK: [%s]" % name
         if is_conditional: