Ported SQL code to Qt
Replaced sigc signals with qt ones
Fixed mysql table creation script
Throw error message if connection is not successful
Added a qbs project file
Removed CMake buildsystem
Fixed missing include

This only worked due to a certain inclusion order.
Added qt-creators .user files to gitignore
Removed not used constant
Use << operator instead of +

This was a clang warning.
Started on forming entities

This classes should only hold data (no logic) so that they
can be shared between all modules / binaries.
Extracted the configuration code into a module

This moves the configuration handling into a seperate library
which is suitable for testing and later dependency injection.
Silenced compiler warnings about unused variables
Extracted the sql access code into a module

This allows exchanging and testing the sql code later.