Build error: Reference PresentationCore could not be resolved

I have a WPF C# application hosted on GitHub attached to Travis. I configured my .travis-ci.yml this way:

language: csharp
solution: FaceDetection/FaceDetection.sln

script:
    - xbuild /p:Configuration=Debug /p:Platform=x86 /p:TargetFrameworkVersion="v4.0" FaceDetection/FaceDetection.sln

However I get these errors when the project is about to compile by travis:

/usr/lib/mono/4.5/Microsoft.Common.targets:  warning : Reference 'PresentationCore' not resolved
/usr/lib/mono/4.5/Microsoft.Common.targets:  warning : Reference 'PresentationFramework' not resolved

Compiling the project locally on my windows machine in VS works fine. Therefore I included all needed references for the project.

This happens to some more references too:

Views/Converters/BitmapConverter.cs(5,28): error CS0234: The type or namespace name `Imaging' does not exist in the namespace `System.Windows.Media'. Are you missing an assembly reference?
Views/UserControls/FaceDatabaseEntry.xaml.cs(7,22): error CS0234: The type or namespace name `Controls' does not exist in the namespace `System.Windows'. Are you missing an assembly reference?
Views/UserControls/FaceDatabaseEntry.xaml.cs(9,22): error CS0234: The type or namespace name `Documents' does not exist in the namespace `System.Windows'. Are you missing an assembly reference?
Views/UserControls/FaceDatabaseEntry.xaml.cs(12,28): error CS0234: The type or namespace name `Imaging' does not exist in the namespace `System.Windows.Media'. Are you missing an assembly reference?
Views/UserControls/FaceDatabaseEntry.xaml.cs(13,22): error CS0234: The type or namespace name `Navigation' does not exist in the namespace `System.Windows'. Are you missing an assembly reference?
Views/UserControls/FaceDatabaseEntry.xaml.cs(14,22): error CS0234: The type or namespace name `Shapes' does not exist in the namespace `System.Windows'. Are you missing an assembly reference?
ViewModel/AddFaceViewModel.cs(13,38): error CS0012: The type `System.ComponentModel.INotifyPropertyChanged' is defined in an assembly that is not referenced. Consider adding a reference to assembly `System.ObjectModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'

The needed packages are restored fine before it is about to compile:

Installing 'PostSharp.Patterns.Model 4.2.27'.
Installing 'System.Data.SQLite.Linq 1.0.101.0'.
Installing 'PostSharp.Patterns.Common 4.2.27'.
Installing 'ZedGraph 5.1.7'.
Installing 'MahApps.Metro 1.3.0-ALPHA160'.
Installing 'MvvmLight 5.3.0.0'.
Installing 'DirectShowLib 1.0.0'.
Installing 'System.Data.SQLite.Core 1.0.101.0'.
Installing 'CommonServiceLocator 1.3'.
Installing 'System.Data.SQLite.EF6 1.0.101.0'.
Installing 'PostSharp 4.2.27'.
Installing 'System.Data.SQLite 1.0.101.0'.
Installing 'OpenTK 1.1.2349.61993'.
Installing 'EmguCV 3.1.0'.
Installing 'OpenTK.GLControl 1.1.2349.61993'.
Installing 'EntityFramework 6.1.3'.

Successfully installed 'PostSharp.Patterns.Model 4.2.27'.
Successfully installed 'PostSharp.Patterns.Common 4.2.27'.
Successfully installed 'DirectShowLib 1.0.0'.
Successfully installed 'MvvmLight 5.3.0.0'.
Successfully installed 'ZedGraph 5.1.7'.
Successfully installed 'CommonServiceLocator 1.3'.
Successfully installed 'OpenTK 1.1.2349.61993'.
Successfully installed 'System.Data.SQLite.Linq 1.0.101.0'.
Successfully installed 'PostSharp 4.2.27'.
Successfully installed 'System.Data.SQLite 1.0.101.0'.
Successfully installed 'OpenTK.GLControl 1.1.2349.61993'.
Successfully installed 'System.Data.SQLite.EF6 1.0.101.0'.
Successfully installed 'EntityFramework 6.1.3'.
Successfully installed 'MahApps.Metro 1.3.0-ALPHA160'.
Successfully installed 'MvvmLightLibs 5.3.0.0'.
Successfully installed 'System.Data.SQLite.Core 1.0.101.0'.
Successfully installed 'EmguCV 3.1.0'.

The versions of mono and xbuild:

$ mono --version

Mono JIT compiler version 4.2.3 (Stable 4.2.3.4/832de4b Wed Mar 16 13:19:08 UTC 2016)

Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
    TLS:           __thread
    SIGSEGV:       altstack
    Notifications: epoll
    Architecture:  amd64
    Disabled:      none
    Misc:          softdebug 
    LLVM:          supported, not enabled.
    GC:            sgen


$ xbuild /version

XBuild Engine Version 12.0
Mono, Version 4.2.3.0
Copyright (C) 2005-2013 Various Mono authors