Ensures Xapian isn't loaded when XAPIANDB is undefined, as well as when defined as an empty string.
xml2db.pl: update links to schema documentation

Thanks to Matthew Somerville for providing an updated link
and information about this.  (The archive.org version seems
to be the best extant copy, even if it's out of date in
some respects.)

Closes #183.
Glossary object is now created per-test to allow modifying arguments. Comments for all tests.
Fix for trailing whitespace and errant tabs.
Letting Composer do its job properly by locking versions to the last updated.
Merge branch 'master' into unit-testing
Merge branch 'master' into unit-testing
Merge branch 'unit-testing' into 30-annotation-filter