Simplify inits/resets in entityclass/mapclass

Instead of using somewhat-obtuse for-loops to initialize or reset these
vectors, it takes up less lines of code and is clearer if we use
std::vector::resize() and std::vector::clear() instead.

desktop_version/src/Entity.cpp

@@ -78,10 +78,8 @@ void entityclass::init()
 
 void entityclass::resetallflags()
 {
-    for (int i = 0; i < 100; i++)
-    {
-        flags[i] = false;
-    }
+    flags.clear();
+    flags.resize(100);
 }
 
 int entityclass::swncolour( int t )