Fix/cas mission2 (#44)

* changed from only units to also statics in targets for CAS

* added statics and update docs

* optimised hull creation and did not group by group

* added cas_mission.png

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Co-authored-by: dutchie032 <dutchie032>
Co-authored-by: ex61wi <tim.rorije@ing.com>

_docs/pages/reference.html

@@ -212,6 +212,7 @@
                     CAS missions involve close air support for friendly ground forces. <br />
                     CAS mission have a special "BattleManager" module added by defualt. This will make blue and red units shoot at eachoter. <br/>
                     This creates a nice effect. <br/>
+                    To see how it's done see: <a href="./tutorials.html#mission-cas">[Tutorials] Mission: CAS</a>
                 </p>
 
                 <h3 id="strike">STRIKE</h3>