Add tiled map, tilesheet configs etc

These are just XML so relatively git-friendly.  They're needed for the
game and should be syncronised to the version of the code so they
really ought to be checked in.

assets/objectsprites.tsx

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<tileset version="1.10" tiledversion="1.11.0" name="objectsprites" tilewidth="80" tileheight="128" tilecount="5" columns="0">
+ <grid orientation="orthogonal" width="1" height="1"/>
+ <tile id="0">
+  <image source="tiled-obj/flag-0.png" width="32" height="64"/>
+  <objectgroup draworder="index" id="5">
+   <object id="5" x="6" y="0" width="26" height="55"/>
+   <object id="6" x="0" y="54">
+    <point/>
+   </object>
+  </objectgroup>
+ </tile>
+ <tile id="1">
+  <image source="tiled-obj/fountain-0.png" width="48" height="48"/>
+  <objectgroup draworder="index" id="2">
+   <object id="1" x="0" y="0" width="48" height="45"/>
+   <object id="4" x="0" y="31">
+    <point/>
+   </object>
+  </objectgroup>
+ </tile>
+ <tile id="2">
+  <image source="tiled-obj/house.png" width="80" height="80"/>
+  <objectgroup draworder="index" id="2">
+   <object id="1" x="3" y="0" width="74" height="77"/>
+   <object id="2" x="0" y="75">
+    <point/>
+   </object>
+  </objectgroup>
+ </tile>
+ <tile id="3">
+  <image source="tiled-obj/tower.png" width="48" height="128"/>
+  <objectgroup draworder="index" id="2">
+   <object id="1" x="0" y="0" width="48" height="112"/>
+   <object id="2" x="0" y="95">
+    <point/>
+   </object>
+  </objectgroup>
+ </tile>
+ <tile id="4">
+  <image source="tiled-obj/waterfall-0.png" width="48" height="64"/>
+  <objectgroup draworder="index" id="2">
+   <object id="1" x="0" y="0" width="48" height="64"/>
+   <object id="2" x="0" y="48">
+    <point/>
+   </object>
+  </objectgroup>
+ </tile>
+</tileset>