[osis-core] The prefix for the element in the attribute "path" of element <workPrefix> be required.

[Todd Tillinghast]

Patrick,

The prefix for the element in the attribute "path" of element 
<workPrefix> be required.

Because OSIS elements must be namespace qualified it makes sense to 
allow only valid XPath for the value "path".  Natually the element 
prefix would need to be declared with an xmlns attribute.

The current regex optionally allows the namespace prefix.

Todd