Allow to override config_dir for graphite::web
Revert "Use native fact for timezone selection"

The complete point of setting the timezone in the configuration file is
to override the system on.

This reverts commit 7b346cb01bfd9750668a6abc2c47f9222824eb62.

Conflicts:
	manifests/params.pp
	manifests/web.pp
	manifests/web/config.pp
Rework a bit how parameter are passed