Remove mime mapping container config

There should not be any Servlet container around which does not support
JSON by default. The backend does not have an AppCache manifest so a
mapping is not needed here either.

src/main/webapp/WEB-INF/web.xml

@@ -70,15 +70,6 @@
 		<url-pattern>/*</url-pattern>
 	</filter-mapping>
 
-	<mime-mapping>
-		<extension>manifest</extension>
-		<mime-type>text/cache-manifest</mime-type>
-	</mime-mapping>
-	<mime-mapping>
-		<extension>json</extension>
-		<mime-type>application/json</mime-type>
-	</mime-mapping>
-
 	<session-config>
 		<tracking-mode>COOKIE</tracking-mode>
 	</session-config>