Modified default callback functions, to control if caller wants array

	modified:   lib/Eixo/Rest/Api.pm
Added 'format' param, to expect other types of content in response

Fix images#create

	modified:   lib/Eixo/Docker/Image.pm
	modified:   lib/Eixo/Rest/Client.pm
	modified:   lib/Eixo/Rest/Request.pm
	modified:   t/040_images_integration.t
	modified:   t/request_async_t.pl
	new file:   t/041_images_manipulation.t