doc/components: add breadcrumb documentation

doc/12-Web-Components-Breadcrumb.md

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+Web Components: Breadcrumb
+==========================
+
+All Business Process renderers show a **breadcrumb** component to always give
+you a quick indication of your current location. 
+
+![Símple Breadcrumb](screenshot/12_web-components_breadcrumb/1201_simple-breadcrumb.png)
+
+The left-most section shows the title of the current *Business Process Configuration*.
+The remaining sections show the path to the current *Business Process Node* currently
+being shown.
+
+Hovering the Breadcrumb with your mouse shows you that all of it sections are
+highlighted, as they are links pointing to either the root level when clicking
+on the *Configuration Node* itself or to the corresponding *Business Process Node*.
+
+All but the last section, showing your current position in the tree. Even if
+not being highlighted, it is still a link an can be clicked in case you neeed
+so.
+
+In case you're showing some related details in a split-screen view of *Icinga
+Web 2*, a click on any *Breadcrumb* section will switch back to a wide single
+column view to make it obvious that you moved to another context. It is also
+perfectly legal to open any of the available links in a new browser tab or
+window.
+
+Available actions below the Breadcrumb
+--------------------------------------
+
+### Choose a renderer
+
+The first link allows to toggle the used Renderer. Currently a *Tree* and a
+*Tile* renderer are available. 
+
+### Move to Full Screen Mode
+
+Every view can be shown in *Full Screen Mode*. Full screen means that left and
+upper menu together with some other details are hidden. Your Business Process
+will be able to use all of the available space. Want even more? Then please
+additionally switch your browser to full screen mode. This is usually done by
+pressing the `F11` key.
+
+Once being in full screen mode you'll find an icon on the right side that will
+allow you to switch back to normal view:
+
+![Símple Breadcrumb](screenshot/12_web-components_breadcrumb/1202_return-from-fullscreen.png)
+
+**Hint:** We know that the web application might request real full screen mode
+on their own. We refused doing so as many people find this being an annoying
+feature.
+
+Other main actions
+------------------
+
+### Add content to your Dashboard
+
+When being in *locked* mode, you are allowed to add the currently shown process
+at the given path with the active renderer in the main (or a custom) Icinga Web 2
+Dashboard:
+
+![Add to Dashboard](screenshot/12_web-components_breadcrumb/1203_add-to-dashboard.png)