add content security policy
add content security policy

-	all external requests will be blocked (including images)
-	inline javascript and styling is still allowed

MPIB/Lagerregal,MPIB/Lagerregal,vIiRuS/Lagerregal,MPIB/Lagerregal,vIiRuS/Lagerregal,vIiRuS/Lagerregal