Update UnitCollection class Remove method.
Merge branch 'master' of https://github.com/toecto/opocraft

Conflicts:
	development/OppoCraft_v1.0/OppoCraft_v1.0/OppoCraft.csproj
	development/OppoCraft_v1.0/OppoCraft_v1.0/Units/Unit.cs
	development/OppoCraft_v1.0/OppoCraft_v1.0/Units/UnitCollection.cs
Update the remover method in UnitCollection class