MFde: Update the German Documentation set.

Several chapters of the handbook are now up-to-date again. Additionally,
two new chapters are freshly translated: filesystems and DTrace.
The following people contributed valuable spelling and grammar fixes to
the translation:

Section about Virtualization with VirtualBox and DTrace chapter: [1]
Section about Link Aggregation: [2]
Filesystems chapter: [3]

de_DE.ISO8859-1/books/developers-handbook/x86: 1.16 -> 1.17
de_DE.ISO8859-1/books/handbook/advanced-networking: 1.414 -> 1.425
de_DE.ISO8859-1/books/handbook/basics: 1.156 -> 1.157
de_DE.ISO8859-1/books/handbook/bibliography: 1.85 -> 1.86
de_DE.ISO8859-1/books/handbook/desktop: 1.75 -> 1.91
de_DE.ISO8859-1/books/handbook/disks: 1.290 -> 1.291
de_DE.ISO8859-1/books/handbook/dtrace: 1.8 (new)
de_DE.ISO8859-1/books/handbook/filesystems: 1.8 (new)
de_DE.ISO8859-1/books/handbook/introduction: 1.134 -> 1.135
de_DE.ISO8859-1/books/handbook/jails: 1.17 -> 1.18
de_DE.ISO8859-1/books/handbook/linuxemu: 1.135 -> 1.137
de_DE.ISO8859-1/books/handbook/multimedia: 1.131 -> 1.132
de_DE.ISO8859-1/books/handbook/virtualization: 1.17 -> 1.19

[1]: Christoph Sold (cs at cheasy dot de)
[2]: Sharon Bahagi (sbahagi at gmx dot net)
[3]: Daniel Seuffert (DS at praxisvermittlung24 dot de)

Obtained from: The FreeBSD German Documentation Project
Approved by: jkois (mentor)