<!--- Verify first that your feature was not already discussed on GitHub -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
azure_rm_galleryimageversion_module should be able to take data disk snapshots as input.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
azure_rm_galleryimageversion_module

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
Starting from SIG api version 2019-07-01, we support creating image version from snapshots, which contains 1 os disk snapshot and 0 to many data disk snapshots. By having this feature, it give customers full power to create image version from snapshots.

Here is a sample request entity:
{"name":"1.0.0","location":"West US","properties":{"publishingProfile":{"excludeFromLatest":false},"storageProfile":{"osDiskImage":{"source":{"id":"/subscriptions/<subId>/resourceGroups/rgName/providers/Microsoft.Compute/snapshots/osSnapshotName"}},"dataDiskImages":[{"lun":0,"source":{"id":"/subscriptions/<subId>/resourceGroups/rg/providers/Microsoft.Compute/snapshots/datadiskSnapshot1"}}]}}}

So for data disk, user needs to provide "lun" and "source".

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can also paste gist.github.com links for larger files -->

else:
                    new = sorted(new)
                    old = sorted(old)
                for i in range(len(new)):
                    if not self.default_compare(modifiers, new[i], old[i], path + '/*', result):
                        comparison_result = False
            return comparison_result
        else:
            updatable = modifiers.get(path, {}).get('updatable', True)
            comparison = modifiers.get(path, {}).get('comparison', 'default')
            if comparison == 'ignore':
                return True
            elif comparison == 'default' or comparison == 'sensitive':
                if isinstance(old, string_types) and isinstance(new, string_types):
                    new = new.lower()
                    old = old.lower()
            elif comparison == 'location':
                if isinstance(old, string_types) and isinstance(new, string_types):
                    new = new.replace(' ', '').lower()
                    old = old.replace(' ', '').lower()
            if str(new) != str(old):
                result['compare'].append('changed [' + path + '] ' + str(new) + ' != ' + str(old) + ' - ' + str(comparison))
                if updatable:
                    return False
                else:
                    self.module.warn("property '" + path + "' cannot be updated (" + str(old) + "->" + str(new) + ")")
                    return True
            else:
                return True