Introduced new "directory" task type
* tasks of this type expect a path node providing the directory tree to be created
** the path is passed to `mkdir --parents $path` which does the actual work
* this addition was introduced to fix failing `create_link` calls in cases where the link is created before the actual directory is created as a side-effect of `InputXSLT:generate`
** this side-effect causes `InputXSLT:generate` to be impure and should be elimniated in InputXSLT if possible
*** the current hindrance preventing me from doing just that are the `xpath` target declarations which depend on this behaviour