More uri-utils functions

 * pf:is-absolute
 * pf:is-relative
 * pf:get-path
 * pf:replace-path
 * pf:unescape-uri
Add a pf:file-exists function to saxon
make p:fileset-store indent XML docs
Fix uri function pf:is-absolute
Merge pull request #12 from daisy-consortium/uri-functions

Uri functions