Restyle and restructure left navigation panel

[foliengriller]

Motivation:
The assignment of information and functional elements should be improved by the transformation and restructuring.

Changes:

• Information concerning the current document is summarized by the dark background.
• The orange background is used for grouping the parent level (documentation server)
• Information and selection of the version is assigned to the title of the document and only displayed if the document exists in several versions.
• The search is clearly recognizable by the magnifying glass icon which also acts as a submit button
• Distances and horizontal alignment improve the visibility of the structure

[sypets]

I'm adding an image to visualize the current status and results for the ideas.

I'm not changing anything of the original ideas, I used the screenshot above and compare it with the current rendering result.

[benjaminkott]

Resolved with #140