Add instance-actions,flavors,flavor-rxtx metafiles for api-samples

Add instance-actions,flavors,flavor-rxtx metafiles for api-samples
    
    Converts instance-actions,flavors,flavor-rxtx api sample to create
    meta files for api sample docs.
    We use this to auto generate the specification document.
    
    And add 'extension_name' for flavors api samples to ensure generating
    'extenion' attribute in metafiles.