Extracted library and console application into separate projects. Closes #3
Allow specifiying input and output files using command-line parameters
All backdrop settings can now be specified on the command-line
Added website demo project
Provide default values for backdrop settings. Closes #5
Added unit tests
Merge branch 'refactoring' of https://github.com/ErikSchierboom/backdrop-creator into ErikSchierboom-refactoring

Conflicts:
	src/BackdropCreator/Backdrop.cs
	src/BackdropCreator/BackdropSettings.cs
	src/BackdropCreator/ImageExtensions.cs
	src/BackdropCreator/Program.cs
	tests/BackdropCreator.Tests/BackdropTests.cs
	tests/BackdropCreator.Tests/ImageExtensionsTests.cs