Bug 877544: Improving find_application

This improves the speed of `find_application` by calling it once with a generated REST endpoint instead of calling `find_domain().find_application()`.
Also added the ability to `:include => :cartridges` in the application request so we don't have to lazy load them later.

Relies on this updated `origin-server` test: https://github.com/openshift/origin-server/pull/1426

### Before
```ruby
# 1 REST request
# Response: domain + all applications
domain = client.find_domain(domain_name);
#  Must iterate through all applications and do string comparison against name
app = domain.find_application(app_name);
# 1 REST request
# Response: all cartridge information
carts = app.cartridges
```

### After
```ruby
# 1 REST request
# Response: domain + 1 application + all cartridge information
app = client.find_application(domain_name, app_name, :include => :cartridges)
# No REST requests, all information already in memory
carts = app.cartridges
```

### Savings
* 1 REST request
* HTTP payloads for N-1 applications
* Memory for storing N-1 applications inside domain object
* O(N) searching through applications for names