A service is function which is executed outside the promise tree when the
gadget is attached to the DOM.
Services are stopped when the gadget is removed from the DOM.

You can declare a service with the "declareService" method, which takes a
function as parameter.

Service errors are reported to the parent gadget by acquisition on
"reportServiceError".
If no gadget catched the service error, the application will crash (document
body will display the raw error).

Do not prevent calling declareGadget in ready functions.
Allow to directly declareGadget inside the HTML.

Only ease to ease developper comprehension.

Drop EventTarget support on Gadget.
Add declareAcquiredMethod, allowPublicAcquisition.
Prefix attribute non part of the API by __. Such method/property can be rename
in next versions without any compatibility support.
Use base element in iframe to get the same link behaviour with or without
iframe.

declareAcquiredMethod generated function should not call local (ie, same
gadget) allowedAcquisition method.

Use declareAcquiredMethod instead.

aq_dynamic was a "low level" method, somehow hard to understand.
Allow acquisition more explicitely by providing the method name allowed.

Replace the gadget method "acquire" by the Klass function
"declareAcquiredMethod" which generates new accessors on this class and do a
direct mapping with the parent aq_dynamic function.

Acquisition will be the only way to propagate informations to the parent
gadget.

It may help developper to see all properties which are not part of the API.

Add methods to fetch an existing gadget from its scope and drop the scope
reference.

Thanks to Thibaut Frain for this patch.