add missing HarvesterAttackNotifier

closes #6671
document HarvesterAttack- and BaseAttackNotifier
Revert cachedLocation change that caused issues with transports.

This partially reverts commit 2f5ac1a360342e180f24ac2289cf34fcb0b21045.
Fix closure issue with mission objectives. Fixes #6680.
Mods.Common Effects

Moved over more effects to Mods.Common
Merge pull request #6687 from pchote/fix-shellmap

Revert "Some minor Cargo style fixes."
Merge pull request #6667 from steelphase-forks/common-effects

Mods.Common effects
Merge pull request #6691 from pchote/objective-duplication

Fix closure issue with mission objectives.
Use the existing SpriteLoader cache for tilesets.
Use SpriteLoader for frame exporting.
Remove --transpose utility command.

The engine has supported transposed sprites for a long time now.
Add plumbing for mod-defined sprite loaders.
Move ShpTD sprite loading into Mods.Common.
Move ShpTS sprite loading into Mods.Common.
Move R8 sprite loading into Mods.D2k.
Move TmpRA sprite loading into Mods.Common.
Move TmpTD sprite loading into Mods.Common.
Move TmpTS sprite loading into Mods.TS.
Move ShpD2 sprite loading into Mods.Common.
Remove the remaining legacy sprite plumbing.