Initialize the accessibility support calling cally_accessibility_init
Take into account that this is required to at least be sure that
CallyUtil class is available.
It also modifies cally_accessibility_module_init in order to return
if the initialization was fine (and the name, removing the module word).
It also removes the gnome accessibility hooks, as it is not anymore
module code.
Solves CB#2098
This commit includes a method to init the a11y support. Two main purposes:
* Register the different Atk factories.
* Ensure that there are a AtkUtil implementation class available.
Part of CB#2097
