Mods.Common Widgets

Moved over Widgets that don't require a bunch of things to move.
Extended IMove for Enter logic
Extend Enter activity class for (re)usability in enter/exit/dock logic
Avoid reading CenterPosition of invalid targets in DamageWarhead

Fixes #6642
Merge pull request #6645 from obrakmann/fix6642_tib_warhead_crash

Avoid reading CenterPosition of invalid targets in DamageWarhead
Fixed #4640 - Units teleport into transports.
Added IDisableMove
Prevent transport from moving while loading cargo
Merge pull request #6528 from atlimit8/DragIntoTransports

Modifies IMove & Enter and Fixes #4640 - Units teleport into transports
Merge pull request #6632 from steelphase-forks/common-widgets

Mods.Common Widgets
Fix crash when husks are spawned by a moving actor.

Fixes #6648.
Merge pull request #6652 from pchote/fix-husk-crash

Fix crash when husks are spawned by a moving actor.
remove BelowUnits

closes #3670