Part 1: 2301239 cleaning up MenuLinkContent.php.
Part 1: 2301239 cleaned up class in MenuLinkContent.php
code comment fixes
return doc fix
document what NULL means
document return values for menu tree storage
Part 1: 2301239 Cleaned up class in MenuLinkContent.php and added type hint in MenuLinkContentInterface.
add an exception if you try to re-create a plugin
add an exception if you try to create an invalid plugin
doxygen fixes