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Adds torch 2.0 compatibility

Deprecate python 3.7

Incorporating #149 and #150 fixing bug preventing save/load of ODEProblem objects ( raised in issue #122).

• Added the ability to explicitly pass parameters in the form of a dictionary at each ODE solver step
• fixed_odeint can now accept dictionaries as state
• added save_at argument to odeint to have the solver save the solution only at specified time instants
• Data control variable u in NeuralODE has been changed to _control
• Added support for Python 3.7
• various bug fixes

torchdyn 1.0 is finally out!

Minor fixes. More prep for 1.0. Updates PyPI installable version of torchdyn.

More tutorials. MultipleShootingProblem is in. Several fixes to the numerics.

Edit with latest fixes.