Add extracting action output

 * In case if we define the specific output
   in action, we should evaluate all given YAQL
   expressions and return calculated dict,
   otherwise - return raw result

Change-Id: I8f4a91c7fb0de743793c7cd66b892e038e25332f
Fix minor issues

 * Action factory creates rest_action with either
   parameters or body accordingly to request method
   (for GET - parameters, for POST/PUT - body)
 * Fix apply context method:
   * All data which is not resolved by YAQL is ignored
 * Rest action send body in form json.dumps(data)
   (it is better for nested dictionary)
 * Improved some unit tests

 * With this patch Mistral is able to connect to Nova
   and create instance

Change-Id: Ibc73a7dc2de4339acbb9310755c2c53028815b38
Merge "Add extracting action output"
Merge "Fix minor issues"