show a user friendly description of the starting unit template

closes #6209
beautify starting unit notification when joining server

move LobbySettingsNotification into it's own ServerTrait
Suppress map change order when selecting the same map.  Fixes #6206.
Merge pull request #6271 from pchote/map-kick-fix

Avoid sending the map change order when selecting the same map.
Merge pull request #6217 from Mailaender/starting-units-classname

Fixed lobby start unit notifications not showing class names
Remove unused method
Ensure that all combatants have a defined WinState at the end of the game
Make ScriptContext available in Actor- and PlayerProperty classes

Needed to return non-native types to Lua
Add OnCapture, OnAddedToWorld and OnRemovedFromWorld triggers to Lua API

This brings the new Lua API up to feature-parity with the old API in the
trigger department.
Add a number of small helper functions to Lua API
Add reinforcements functions to Lua API
Adjust gdi01 to use new functions