Allow to disable url caching during development

Right now In-Portal has rewrite listener system that allows to build some amazing urls with ease.

But each url is cached in CachedUrls table (for performance reasons), which makes it hard to implement changes in rewrite listeners during development because cached version of rewrite listener is used instead of one, changed by developer.
Of course there is corresponding "Reset" button in "Tools -> System Tools" section, but it's maybe inconvenient to use, especially when you make a lot changes to rewrite listeners.

I'm proposing to add new DBG_CACHE_URLS option into $dbg_options array of /system/debug.php file that would allow to enable/disable url caching while in debug mode.