Made the locked property non-required.
This makes it easier to generate a Form that can properly deal with GradingRecords. Since required boolean properties can only be set to true by such an automatically generated form.
# use glob syntax.
syntax: glob
*.pyc
*.zip
*~
.project
.pydevproject
app.yaml
build
tests/coverageResults
*,cover
tests/.coverage
*.git
*.egg-info
eggs
parts
.installed.cfg
bin
develop-eggs
.gitignore
.DS_Store
.settings