As this button leads to a void form view without context it is not
really usefull. As creating new records is achieved using aliases
there is no real need for a New Task/Issue/Note button.
mail/new controller is kept for compatibility but should be removed
before v11.
There is now a single method easier to inherit to add specific behavior
for the display of access button as well as actions buttons. All addons
using this mechanism are updated accordingly.
stage_id is comptued and based on stage_ids
The default value should be put on stage_ids, not stage_id, it has the same
effect but avoids an unecessary chain update.
Christophe Simonis