Facilitated spawn choice at game setup screen.
    Bigger spawn points, numbers within.
Smaller spawns+letters. Map dialog width. Unavailable spawns disabled.
The engine now uses the SDL2.0 scroll events properly.

Scroll speed is now a user preference.
fix neighbored walls connecting to everyhing

closes #5232
Fixes AI units hunting down Missile Silo/Temple of Nod after being damaged by nuke
Fixes units hunting Advanced Comm. Center after being damaged by Ion Cannon.

Additionally made weapon, effect animation and effect palette customizable.
Merge pull request #5329 from reaperrr/nuke-ion-fix

Closes #5239
Merge pull request #5326 from Mailaender/wall-types

Fixed sandbags connecting to concrete walls
Merge pull request #5297 from Saticmotion/betterScrolling

Better scrolling
Merge pull request #5192 from matija-hustic/spawnchoice

Spawnchoice
don't show order lines when selecting idle (attackmoving) actors

closes #5039