Removing projects field from component view and filtering the activities...

... and milestones by project when creating task from component view + bugfix

* When creating task from a project, project field should not show and the activities, milestones should be filtered list for that project.
* bugfix in change_password
I get it now, i'll have a remove_element(self, selector) function in S3SQLCustomForm class which removes the element with the selector name given as argument and then call crud_form.remove_element("task_project") from the controller. Is this correct?