fixes #3708 Allow Cache-Control to be set on SpeedyAssetServlet
Update dotmarketing-config.properties

#3708
Update SpeedyAssetServlet.java

#3708
Update SpeedyAssetServlet.java
Merge pull request #3801 from dotCMS/issue-3708-allow-cache-control-to-be-set-on-SpeedyAssetServlet

fixes #3708 Allow Cache-Control to be set on SpeedyAssetServlet