levels: The great FreeDM level reordering.

This commit applies a new ordering for FreeDM's levels, designed by Protox
and preserving the existing names and music used for the levels.
This Doomworld thread has some more information:
http://www.doomworld.com/vb/freedoom/69435-proposed-map-lineup-for-freedm/

Five of the existing levels were moved as they were judged not to meet
quality standards.

Summary of changes:

DM01 - Renamed to DM01
DM02 - Removed
DM03 - Renamed to DM15
DM04 - Renamed to DM08
DM05 - Renamed to DM27
DM06 - Renamed to DM18
DM07 - Renamed to DM07
DM08 - Renamed to DM10
DM09 - Renamed to DM28
DM10 - Renamed to DM13
DM11 - Removed
DM12 - Renamed to DM14
DM13 - Renamed to DM02
DM14 - Renamed to DM21
DM15 - Renamed to DM29
DM16 - Renamed to DM22
DM17 - Renamed to DM24
DM18 - Renamed to DM03
DM19 - Removed
DM20 - Removed
DM21 - Renamed to DM06
DM22 - Renamed to DM25
DM23 - Renamed to DM12
DM24 - Renamed to DM11
DM25 - Renamed to DM09
DM26 - Removed
DM27 - Renamed to DM17
DM28 - Renamed to DM23
DM29 - Renamed to DM04
DM30 - Renamed to DM30
DM31 - Renamed to DM16
DM32 - Renamed to DM26
DM33 - Renamed to DM05
DM34 - Renamed to DM31
DM35 - Renamed to DM32
levels: Add new DM19, DM20.

These two new levels by Protox bring the FreeDM level count back up to
the full 32 again, after the great renaming.
levels: Fix up FreeDM levels.

This tweaks a bunch of FreeDM levels and fixes several known bugs
in them.

Issues fixed:
- Fixes #23 (DM01 lighting level).
- Fixes #61 (DM13 nonfunctional teleport).
- Fixes #75 (DM14 rockets explode behind teleport lines).
- Fixes #26 (DM02 tutti-frutti).
- Fixes #7 (DM24 HoM).