Improvements to the instance creation

With all the different hypervisors supported and with each hypervisor have a list of parameters. Horizon need a way to set this parameters. Example: We could set the video drivers in most hypervisors. But the parameter is different for each VM.

What I suggest is to implement a key/value structure of all possible values in the form of [hypervisor][option][parameter]= value. The value is what will be passed to nova.

Example
{'KVM':
  'video_driver':{'vga': 'hw_video_drv=vga', 'cirrus': 'hw_video_drv=cirrus' },
  'video_memory_range': ('hw_video_memory': '1:10:1'),
 ...
}}

The type of values we can represent are dictionaries and numerical ranges

In the create instance form, we could dynamically populate the form with [option][parameter]. We must make sure that the keys of [option][parameter] matches for every [hypervisor].

So far, nova need to update the image meta-data before spinning up a instance.