Updates for 2.7.1 release

Doc fixes for release

Updates for 2.7.0 release

Fixes #902 - ensure leaf keys in groupings are marked as such

Fixes #914 - scan comments iteratively

Fixes #930 - allow dot in if-feature expression

fixed merge errors

Merge branch 'knollpoi-add-flatten-rootmodule'

Fix incorrect error message when using UML option --uml-no=identity

Fix uses attributes in a class not being hidden when using UML option --uml-classes-only

Revert fix for classesonly

Fix uses attributes not being suppressed when using --uml-classes-only

Initial fix

Plugin sid: Reintroduction of test 24 ietf-system

Plugin sid: Assign SIDs to choice and case nodes