* support DTD modification
* better support for namespaces
+ allow entity reference insertion
* allow parameters for user defined functions
* split element
* 'locate' - allow use also nearest id() 
+ external xinclude save support
* untag/split element
* comment-out node (?? uncomment ??)
* fold/unfold command (fold/unfold elements for subsequent ls commands)
* xsh-grammar: parse xslt parameters as XPATH instead of XSH expressions ??
