More changes to make the tile cache directory configurable at runtime

* -t|--tile-dir option for render_list and convert_meta
* renderd reads it from renderd.conf section "[renderd]" setting "tile_dir"
* mod_tile reads from Apache conf ModTileTileDir directive
There are still some places in store.c left, where HASH_DIR is used directly. More fixes needed.

daemon.h

@@ -20,6 +20,7 @@ typedef struct {
     char xmlname[XMLCONFIG_MAX];
     char xmlfile[PATH_MAX];
     char xmluri[PATH_MAX];
+    char tile_dir[PATH_MAX];
 } xmlconfigitem;
 
 #endif