Fix event/alarm types in UDDF export.

UDDF only supports a specific set of alarms. Some events also don't map
to alarms but map to other types of elements in UDDF.

This patch adds a map of the accepted types. Where a map doesn't exist
the type will not be mapped to an alarm, the option then remains to
map it to another kind of element, in the same way that happened with
headings and gas switches.

This removes the need for the specific exclusion of heading and
gas switch, as they are now simply not included in the map.

Signed-off-by: Martin Long <martin@longhome.co.uk>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>