Remove xspace package

From the developer of the package: "personally I wouldn't recommend it".

> The original version used a very simple nested test for following punctuation,
> but it could get the test wrong in some (well rather a lot really) of cases.
> Morten made the tests a lot better so the current version makes the correct
> choice in more cases and is more easily customised, however making the tests
> more complicated highlights the problem with this kind of package.
>
> The rule in TeX is really quite simple, after a command name that uses letters
> (as opposed to single character command names using non-letters such as \$)
> white space is ignored. It is easy to forget to use \ or {} but the result of
> forgetting is very predictable, you lose white space in the result.
> Conversely with xspace the macro will get the correct space most of the time,
> but it isn't easy to predict when it will get it wrong, and so it's much harder
> to learn to enter the markup in a way that is always correct rather than having
> to always visually check for missing space, which rather negates the purpose of
> the command.
>
> So, if you find it useful, fine, it's there.
> But personally I wouldn't recommend it
>
> -- David Carlisle on [Stack Overflow](https://tex.stackexchange.com/a/86620)

thesis.tex

@@ -80,7 +80,6 @@
 \sethyperrefhhucolors{} % Setzt den Farbsatz der HHU für hyperref.
 \usepackage{url} % \url Kommando für Darstellung von Links
 \usepackage{csquotes} % Improved quoting.
-\usepackage{xspace} % Nicht terminierte Kommandos essen keinen Whitespace mehr.
 
 %% Tabellen
 \usepackage{tabularx} % tabularx Umgebung für mehr Kontrolle über Tabellen.