Fix chapter label names to no longer use generic name with number.

Fix chapter label names to no longer use generic name with number.
Now basically use name of the file as part of the chapter label.
This makes it more clear for following or creating new cross-references.

Note that most of the labels were not even used.

This also fixed two previously broken references in license.tex.
And fixed two chapters that had identical label (oldfileset and mysql).

(No changes to content.)