*Title: Make interface to ezmedia datatype similar to ezbinaryfile

Incentive:
The ezbinaryfile datatype provides the 'filesize' and 'filepath' attribute
to the template language while ezmedia does not. Attribute which relate
directly to files should be the same in media and binaryfile.

*Documentation:
The ezbinaryfile datatype now has two new attributes called 'filesize' and
'filepath' which behave in the same way as the attributes in ezbinaryfile.

Example template usage:
filesize: {$attribute.content.filesize|si( byte )}
filepath: {$attribute.content.filepath}