Assorted cleanup for 0.7.4.

- Exceptions reported by tools weren't being reported at the end. 
  This is an old bug. Reporting is now working again.
- Exif video stylesheet had a typo that invalidated it. Fixed.
- Deleted obsolete fits_output_tech_elements.xsd
- Deleted fits.out.xml, which had been added by accident
- If a tool constructor throws an exception, the tool initialization 
  loop now just drops the tool instead of terminating FITS.