Release 4.4.3 Bug Fixes and Small API Change

• Make embedded schema loader tolerate blank sheets by producing
  a warning and returning None instead of raising a StopIteration exception.
  Tweak the Data validation demo to handle the None-instead-of-schema feature.

• Changed cobol.COBOL_file.row_get() to leave trailing spaces
  intact. This created a problem of trashing COMP items that had values
  of 0x40 exactly -- an EBCDIC space.

This second change is an API change. It may disrupt applications that expected stripping of USAGE DISPLAY fields.

It was inappropriate for COBOL_file to be stripping trailing spaces. That's an applications' responsibility.