Updated docstring for ``orm.Entity.Meta``.

The docstring was outdated so I've updated it.
Added ``Ping`` and ``Status`` entities.

I have added the following new Foreman entities:

* ``Ping``

```python
{u'services': {u'candlepin': {u'duration_ms': u'47', u'status': u'ok'},
  u'candlepin_auth': {u'duration_ms': u'41', u'status': u'ok'},
  u'elasticsearch': {u'duration_ms': u'30', u'status': u'ok'},
  u'katello_jobs': {u'duration_ms': u'45', u'status': u'ok'},
  u'pulp': {u'duration_ms': u'16', u'status': u'ok'},
  u'pulp_auth': {u'duration_ms': u'34', u'status': u'ok'}},
 u'status': u'ok'}
```

* ``Status``

```python
{u'release': u'Katello',
 u'timeUTC': u'2014-07-25T19:43:21Z',
 u'version': u'1.5.0-27.el6sat'}
```

Since these new entites only expose a ``GET`` method, there's no need to
define their fields.
One more tweak to ``orm.Entity.Meta`` docstring.
Fix docstrings

If the ".html" extension is omitted, then the linked-to-page will only show a
single path/method combination. If the ".html" extension is added, the
linked-to-page will show all available path/method combinations for an entity.
Merge pull request #1102 from omaciel/new-entities

New entities and docstring change
Merge pull request #1103 from Ichimonji10/docs

Fix docstrings
Flesh out the ComputeResource entity

When creating a new "compute resource" entity, a variable set of values must be
provided to the Foreman server. The exact set of values depends on the specified
provider. (e.g. EC2, Rackspace, etc.) Flesh out the ComputeResource entity with
logic necessary for handling this variability in requirements.
Add some API tests for the ComputeResource entity

All tests for the ComputeResource currently fail. These tests fail for a variety
of reasons. For example:

* Creating a compute resource with a provider of 'Rackspace' causes Foreman to
  throw an HTTP 500 with the message "undefined method `upcase' for
  nil:NilClass".
* Creating a compute resource with a provider of 'GCE' fails because Foreman
  needs more data. However, the types of data needed are not discussed in the
  API docs.
* Creating a compute resource with several other providers causes Foreman to
  return the following error: "getaddrinfo: Name or service not known".

These issues should be tackled by someone who knows a bit more about how compute
resources work.