Added German localization

[Rurido]

Added German localization for the following projects:

• ArcFormats
• GameRes
• GARbro.GUI

There was also a spelling error here which is now fixed.

I also added localization for the menu entry "Troubleshooting"; the dialog box has not been changed.

The commit does not include changes made to the .csproj-files, because I needed to change some stuff to get the projects running. These changes might be useful though:

<EmbeddedResource Include="Strings\arcStrings.de-DE.resx" /> in ArcFormats.csproj
<EmbeddedResource Include="Strings\garStrings.de-DE.resx" /> in GameRes.csproj
<EmbeddedResource Include="Strings\guiStrings.de-DE.resx" /> in ARbro.GUI.csproj