Fixes #5654 by removing false damage states which caused invisible walls

Removes final set of 16 sequences for all walls as it appears that these
are not actually supposed to be used as damage states for the actual
wall, but as end pieces for each wall.  One of the pieces in particular
caused a single wall to be seen as invisible.  Fixes #5654
Add beacon to parabombs, and quantise facings.
Remove obsolete BeaconDuration definitions.
Remove the obsolete flare definition from AirstrikePower.
Use AirstrikePower for spy planes.
Add a spy plane beacon, and quantise facings.
fix a NullReferenceException in preview.Map
Fixed ref and palace footprints.
Merge pull request #5856 from MustaphaTR/d2k-footprints

D2k Some Footprint Fixes
Merge pull request #5854 from pchote/ra-poster

Add beacons to the RA spy plane and parabombs
Use a shared url for news updates. Fixes #5603.
Reorganize news parsing.  Fixes #5647.
Merge pull request #5835 from Squiggles211/wall-damage

Removed false damage states which caused invisible walls.  Fixes #5654
Merge pull request #5840 from Mailaender/map-download-isometry-nre

Fixed a NullReferenceException in auto map download.
Merge pull request #5860 from pchote/news-fix

News fixes
Overhaul ParatroopersPower:

- Adds support for multiple drop planes.
- Adds support a beacon and camera.
- Prevents the plane from circling if it can’t unload.
Fix the crate drop.
Merge pull request #5859 from pchote/paratrooper-cleanup

Improve paratroopers.