First version of nova_config type integration in the module

Hi,
This is a first version using the nova_config type as in the puppet modules of nova. In the last meeting I told you that there were no extra dependencies...but... I was wrong, this adds a new dependency on cprice404/inifile.

The patch makes possible to change the conf file with the following definition:
```
nova_config {
  'DEFAULT/compute_driver': value => 'nova.virt.hyperv.driver.HyperVDriver';
} 
```