xsd-fu: Allow command dependency introspection

- Split verbose option into separate --print-depends and
  --print-generated options
- The --print-generated option behaves the same as the existing
  --verbose option
- The --print-depends option is similar, but rather than printing
  generated source filesnames as they are written, it outputs all
  read files (schemas, templates and template fragments) for the
  command which was run
- Both options may be used with --dry-run to introspect file usage
- Documentation updated to include these new options
- ant and maven builds use --print-generated to preserve existing
  behaviour
- cmake build uses --print-generated to preserve existing behaviour,
  but additionally uses --print-depends to generate correct build
  rules such that if any template or schema file is changed, the
  correct set of source files will be regenerated and rebuilt on
  the fly