Urgent optimization fixes

[kelvinburke]

Fixes:

• Money optimizations throwing a 0/0 error, fixed by ensure dtype of array is float (which can output a warning but it's not an error - the array is sanitized directly afterwards)
• Constraints not being followed: reorders programs so they match the order given by the constraints - also calls programs by their key, not their index to avoid similar problems in the future
• adds a reorderprograms to the Programset class
• Noteably this does NOT change constrainbudgets behaviour (that commit https://github.com/optimamodel/optima/commit/42b4ee3e3f0a24ebdbfc57281b76144da9be9220 has not been included)