Added "type" to the value_list_t struct.

Added "type" to the value_list_t struct.

This way, the complete tuple (host, plugin, plugin instance, type, type
instance) is stored in a single data-type which is more straight forward
and allows a more flexible use of that data-type. As a consequence, there
is no longer a need to explicitly pass the type to some functions, most
notably plugin_dispatch_values(), which have been updated in that respect.

The "perl" plugin has also been updated to reflect this change. For
backwards compatibility, plugin_dispatch_values() still accepts a second
argument - however, a warning will be submitted to the daemon in that
case.

Signed-off-by: Sebastian Harl <sh@tokkee.org>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>