Remove no-cache header for xml schema files

Validation of XML files in Eclipse is slow because the schema files are downloaded over and over again. This is because the server returns the no-cache header. I think there is no reason for this.

Examples of affected urls:
http://jboss.org/j2ee/dtd/service-ref_4_0.dtd
http://jboss.org/schema/arquillian/arquillian_1_0.xsd
http://jboss.org/ironjacamar/schema/ironjacamar_1_0.xsd
http://docs.jboss.org/ironjacamar/schema/datasources_1_0.xsd

I don't have a definitive list, perhaps rob.stryker could help here.