With this graph, it is hopefully possible to see where (i.e. towards which zoomlevel) most of the rendering time goes,
and thus might give some indication where optimisations in the style sheet are best focused at, if performance is an issue.
It useses purely wallclock time and thus does not account for individual resources.
For large setups of mod_tile, and renderd, it may be beneficial to have a reverse proxy infront of the main tile server.
However when using a fast updating db e.g. running off the minutly diffs, the proxy may either deliver stale content, or the
cache expiry has to be set very short, which limits the effectiveness of the proxy. Instead, this patch adds an explicit
mechanism to renderd to signal to the proxy which tiles have been rerendered and thus should be discarded from the cache.
* -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.
Made renderd more configurable at runtime: socketname, num_threads and the mapnik settings plugins_dir, font_dir, and font_dir_recurse are now available through renderd.conf
There should be only one incompatible change: the [Default] section in the config is now in all lowercase "[default]" because the parser lib gives section and key names back in lowercase
