Make block movement announcements consistent

Use the terms "left" and "right" rather than "backward" and "forward"

Author: sbates-idrc

src/messages.json

@@ -33,8 +33,8 @@
         "Announcement.backward1": "backward 1 square",
         "Announcement.backward2": "backward 2 squares",
         "Announcement.backward3": "backward 3 squares",
-        "Announcement.cannotMoveNext": "At the end of the program, unable to move forward",
-        "Announcement.cannotMovePrevious": "At the beginning of the program, unable to move backward",
+        "Announcement.cannotMoveNext": "At the end of the program, unable to move right",
+        "Announcement.cannotMovePrevious": "At the beginning of the program, unable to move left",
         "Announcement.cannotReplaceLoopBlocks": "cannot replace \"beginning of loop\" or \"end of loop\" blocks",
         "Announcement.control": "control",
         "Announcement.delete": "deleted {actionType} {actionName}",
@@ -559,8 +559,8 @@
         "Announcement.backward1": "reculer d'un carré",
         "Announcement.backward2": "reculer de 2 carrés",
         "Announcement.backward3": "reculer de 3 carrés",
-        "Announcement.cannotMoveNext": "à la fin du programme, incapable d'avancer",
-        "Announcement.cannotMovePrevious": "au début du programme, incapable de reculer",
+        "Announcement.cannotMoveNext": "à la fin du programme, incapable de déplacer vers la droite",
+        "Announcement.cannotMovePrevious": "au début du programme, incabable de déplacer vers la gauche",
         "Announcement.cannotReplaceLoopBlocks": "ne peut pas remplacer les blocs « début de boucle » ou « fin de boucle »",
         "Announcement.control": "contrôle",
         "Announcement.delete": "{actionType} {actionName} supprimé",