Changes to the tutorial + Removal of conditions on prerequisites (adding a condition on tasks other than subtasks preventing subtask prerequisites) + Addition of a condition for a unique common task symbol in a role + Fix clean-dialog text

margin in mat-menu / new tooltips / replace purger by effacer / fix add role dialog message  / zoomin and zoomout with buttons / click on a piece show details + remove icon button to show detail / set font-family everywhere

fix: prerequires panel no longer close automatically + clear task now clear the prerequires too + clear role now clean the prerequired ressources in tasks