motis2: Don't rely on START and END pseudo place names

As the START and END names are considered implementation
details in MOTIS and reflects the internal search direction
instead always use the entered search term for departure of
first leg and arrival of final leg, when these are non-transit
legs.

See: motis-project/motis#703

src/transitplugins/motis2.js

@@ -173,8 +173,10 @@ export class Motis2 {
             departureTimezoneOffset === arrivalTimezoneOffset ?
             departureTimezoneOffset * 1000 : null;
         const legs =
-            itinerary.legs.map(leg =>
-                               this._parseLeg(leg, startPlace, destinationPlace,
+            itinerary.legs.map((leg, index) =>
+                               this._parseLeg(leg, index === 0,
+                                              index === itinerary.legs.length - 1,
+                                              startPlace, destinationPlace,
                                               commonTimezoneOffset));
 
         return new Itinerary({
@@ -188,7 +190,8 @@ export class Motis2 {
         });
     }
 
-    _parseLeg(leg, startPlace, destinationPlace, commonTimezoneOffset) {
+    _parseLeg(leg, isFirst, isLast, startPlace, destinationPlace,
+              commonTimezoneOffset) {
         const isTransit = leg.mode !== 'WALK';
         const distance =
             leg.distance ?? (!isTransit ?
@@ -204,8 +207,8 @@ export class Motis2 {
             commonTimezoneOffset ??
             this._getTimezoneOffset(arrival, this._getTimezone(leg.to.lat,
                                                                leg.to.lon));
-        const from = leg.from.name === 'START' ? startPlace.name : leg.from.name;
-        const to = leg.to.name === 'END' ? destinationPlace.name : leg.to.name;
+        const from = isFirst && !isTransit ? startPlace.name : leg.from.name;
+        const to = isLast && !isTransit ? destinationPlace.name : leg.to.name;
 
         const polyline =
             leg?.legGeometry?.points ?