This commit, refactor the dialog api (dialog.js), to easier the creation of dialog subclasses; force the use of dialog subclass when calling the dialog service; forbid the use of dialog itself and promotes the use of dialog subclasses. closes odoo-dev/odoo#871 Related: odoo-dev/enterprise#151 Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>