(type of filter is indicated in title and description already).
- docbook/item-skel.onefile: updated the template to current practice
- glossary/ITL: added one more part from ictags-more.txt (the section on
quoting of looping subtags)
- glossary/*, refs/DirectoryIndex: little fixes
- refs/*.filter: documented few filters to see how it plays out.
Also prepared the ground to test online examples on them.