Add doc module (WIP)

refs #4820
Modules/doc: Replace Michelf/Markdown with Parsedown

refs #4820
Modules/Doc: Add doc display per module

refs #4820
Modules/Doc: Use Icinga\Web\Menu for the toc

refs #4820
Modules/Doc: Set rel="nofollow" on header links missing a user-specified id

refs #4820
Fix documentation

refs #4820
Modules/Doc: Add Syntax highlighting for PHP code

refs #4820
Implement register and run php scripts for modules

refs #5597
Fix: Missing class in GeneralFormTest
Fix LoggerTest

fixes #5561
Implenent TopBar hook and status summary as hook in monitoring

refs #5597
Merge branch 'feature/hook-and-topbar-5597'

resolves #5597