Raw copy files with invalid extensions.

[ghost]

This changeset modifies the build process to copy over all files with invalid extensions as they are. Due to this change, it is possible to keep content images, videos etc. inside the wiki folder. This is useful for two reasons:

• Easily reusable templates: The templates keep their layout-related files in static. Since no content files are kept in the same folder, it can be copied without cleanup work.
• Permissions: Wiki editors need write access only to the wiki folder and not static. Apart from the maybe not so important security benefit is the fact that they cannot accidentally change the static files for the layout.