Always init pointcache frame step to 1.

Note it was already the case for many simulations (cloth, rigidbody, etc.), just doing this
systematically in BKE_ptcache_add() now, will avoid us some recurring bug reports.
Advanced users will know when they can/have to raise this parameter!

source/blender/blenkernel/intern/pointcache.c

@@ -3000,7 +3000,7 @@ PointCache *BKE_ptcache_add(ListBase *ptcaches)
 	cache= MEM_callocN(sizeof(PointCache), "PointCache");
 	cache->startframe= 1;
 	cache->endframe= 250;
-	cache->step= 10;
+	cache->step = 1;
 	cache->index = -1;
 
 	BLI_addtail(ptcaches, cache);