- following the migration of the document parsing code from array.py, param.py, table.py and lsctables.py into ligolw.py proper, it is no longer necessary to create application-specific content handlers.  the kind of customization that was being done in the past is now impossible.
- therefore, load_fileobj() can now assume a sensible default content handler
- all programs are updated accordingly, example code in documentation is updated accordingly
- because the APIs have now drifted too far, it is no longer possible to continue using the glue package to provide backwards compatible support for documents containing ilwd:char based tabular data.  this (now broken) feature is removed from the programs that were still providing it, and glue is removed from the package dependency metadata.