Four PRs merged into devel

[Edward K. Ream]

PR #4957 ensures that all commands have a docstring.

PR #4958 restores the Plugins:qt_layout sub-menu. It also enables (in leoSettings.leo) the qt_layout plugin by default. You might want to update your myLeoSettings.leo file.

PRs #4964 and #4965 update Leo's required dependencies. These PRs set the stage for issue (RFC) #4891.

Please keep testing the main branch.

Edward