New Visualisation

• Replaced the gl library with the improved VFRendering library: https://github.com/FlorianRhiem/VFRendering
• Added a few UI capabilites, such as minimizing the control bar, controlling spin size, ...
• Added surface visualisation (still unfinished)
• Added IPS information to status bar, improved output
• Added choice of scalar type and other CMake improvements

Improvements, cleanup, new visualisations and plots

• Added Plotting of Energy data (including interpolated values) using QTCharts, requiring QT5.7
• Added Isosurface visulisation and other improvements
• The MMF method now works for the single-spin case
• More API functions, better separation of core and UIs
• Cleaner thirdparty usage, including qhull as external project

Initial release of Spirit

This release should generally work, but graphs and the MMF method are missing and there might be a few bugs.