Pint or sympy for scaling

[bknight1]

I have been playing around with scaling in sympy and have got the functionality pretty close to our pint implementation. Before I make it backwards compatible, do we want to move to sympy? I think It would make attaching units to symbols/expressions a lot easier.

I've attached a script showing my current implementation to dimensionalise/non-dimensionalise units.

Cheers

pint_to_sympy_scaling.ipynb

[bknight1]

New branch BK-sympy_units should allow a straight swap from Pint to sympy.

Here's a notebook

pint_sympy_backwards_check.ipynb

showing the backwards compatibility