Replace "type=teleport" by "type=custom" in maps

The flare-engine complains about any events, which have no special
action attached to them, but are different from 'custom'.
See commit 1593b5a93ae2dec2e66195481177b8d6f35a7030 in flare-engine
for detail.

This commit replaces any teleport events in the maps by custom events.