settings: Don't allow dots in section/key names anymore

This requires config changes if filelog is used with a path that
contains dots. This path must now be defined in the `path` setting of an
arbitrarily named subsection of `filelog`.  Without that change the
whole strongswan.conf file will fail to load, which some users might
not notice immediately.

scripts/settings-test.c

@@ -81,7 +81,6 @@ static void print_section(section_t *section, int level)
 
 /**
  * Recursively print a given section and all subsections/settings
- * FIXME: Doesn't work properly if any of the keys contain dots
  */
 static void print_settings_section(settings_t *settings, char *section,
 								   int level)