Refactor library to use float32 instead of float64 whenever possible

[Xkonti]

Operations on float64 are more expensive than on float32. The library should be refactored so that float64 is as limited as possible. Things to consider:

• cost of converting from float64 to float32 to perform further operations. It might be cheaper to continue with float64 in between areas where float64 is required.
• If the return type of the function is not float64 the conversion cost might be considered free as it would need to happen at some point anyway.