Replace p:episode with p:system-property

I suggest that instead of having p:episode, we have p:system-property
as per XSLT:

Function: String p:system-property(QName)

The QName is expanded into a name using the namespace declarations in
scope for the expression. The system-property function returns a
string representing the value of the system property identified by the
name. If there is no such system property, the empty string must be
returned.

Implementations must provide the following system properties, which
are all in the XProc namespace:

  * p:version, a number giving the version of XProc implemented by the
    processor; for XProc processors implementing the version of XProc
    specified by this document, this is the string "1.0"

  * p:vendor, a string identifying the vendor of the XProc processor

  * p:vendor-uri, a string containing a URI identifying the vendor of
    the XProc processor; often this is the home page of the vendor's
    Web site.

  * p:episode, a string which should be unique for each invocation of
    the XProc processor.

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | We are thinking beings, and we cannot
http://nwalsh.com/            | exclude the intellect from
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