Primitve type: filename

Filenames are regular [[type:string]]s, pointing to a file.
There are two types of filenames, relative and absolute:
! Syntax				Description
| <tt>path/to/file</tt>			A relative file, this is retrieved from the current package.
					i.e. for a filename in a stylesheet, the file is retrieved from that stylesheet.
| <tt>/package/path/to/file</tt>	An absolute filename includes the name of the package. This is a package somewhere in the MSE data directory.

Don't forget the double quotes (@""@) in scripts.
