fixes #5537: it's possible to specify menu item url directly now

fixes #3903 - fixed menu links when relative URLs are set

fixes #3930 - refactoring of edit_self implementation.

fixes #3790 - Added support for isolated engine to foreman menu

fixes #3820 - adds exception output to menu item authorization check

refs #3510 - ensure rescue statement works

fixes #3510 - plugin interface for registering a plugin, updated menu system