Portals; Running from "Test" button builds up temporary files for resources such as CSS files

Running a Portal from the "Test" button on the Portals form leaves temporary files for resources such as CSS files. These files gradually built up over time since they were suffixed by an incrementing number, e.g., CC_CSS-14.css.

Previous versions of these files are now deleted meaning that there should only ever be a maximum of two files for each resource (the unprefixed version and the newly created, prefixed version).