Install icingacli and bash completion in Vagrant VM

fixes #6264
refs #5803
sidebar/menu: menu should be scrollable

This allows us to scroll menus not fitting into available screen height.
Plays nice with menu hovering, however once you scroll down your menu
you'll temporarily disable the hover-menu-feature.

fixes #6283
Modules: Don't call `FrontController::getRoute()' twice

refs #6303
modules/doc: Show nothing on index yet

Before, doc's IndexController::indexAction() showed the documentation
of Icinga Web 2 but index should rather show an overview of available
docs.

refs #4820
modules/doc: Add partial for displaying doc and toc

refs #4820
modules/doc: Rename DocParser::getDocumentation() to getDocAndToc()

refs #4820
modules/doc: Add route 'modules/doc/icingaweb' to display Icinga Web 2's documentation

refs #4820
modules/doc: Replace Parsedown's decprecated method parse() with text()

refs #4820
modules/doc: Rename populateView() to renderDocAndToc()

Rename populateView() to renderDocAndToc() since the method now sets the viewHelper
to docandtoc.phtml

refs #4820
modules/doc: Implement doc/module/$moduleName URLs

refs #4820
modules/doc: Remove icingaweb/index.phtml since it's replaced by renderDocAndToc()

refs #4820
modules/doc: Remove module/view.phtml as it has been replaced by renderDocAndToc()

refs #4820
modules/doc: List available documentations on index

refs #4820
modules/doc: Reduce tab size to two spaces in module/index.phtml

refs #4820
modules/doc: Tell which doc directory does not exist, in case it does not exist :)

Thanks Michael

refs #4820
modules/doc: Add styles

refs #4820
modules/doc: Fix toc links

The DocParser generates toc links with a hard-coded URL. This should
be changed to be generated from a route. But we did not decide how
to handle route overrides yet.

refs #4820
Add Module::addRoute() to add a route to the route chain

refs #6303
Doc: Construct parser with the path to the documentation

Before, the parser decided which path to used based on a given module name.
Now, the parser requires the path to the documentation.
Further the toc items no longer include a URL. The must URL must be generated
from a render function or view script.

refs #4820
Doc: Rename `Controller' to `DocController'

refs #4820