v3.2.0 - First official release

Lots of changes to prepare for first official release.

Main features:

• All dependencies are now opensource
• The docs were completely overhauled to make the code friendlier on new users
• Rewrote all examples

Soft breaking changes:

• Make FLOWVPM a hard dependency
• Fix lots of small bugs
• Advance BPM to v2.0.1

Other features

• Add functions for processing vtks
• Concatenate monitors
• Postprocessing: write postprocess_statistics and postprocess_bladeloading
• Write generate_preprocessing_fluiddomain_pfield
• Add identity matrix