Adding Stochastic Gradient Descent based hologram calculation

[kaanaksit]

Odak supports torch based hologram calculation routines. Odak.learn.wave lacks a definition that can calculate holograms using Stochastic Gradient Descent. The latest and greatest in combining torch and odak is at a branch called torch_1_8_0. At the time of the writing of this issue, any development should go on top of that branch.

• [x] Add a stochastic_gradient_descent definition to odak.learn.wave.classical.
• [x] Add a test script to test folder to run a test for the new added stochastic_gradient_descent definition.

[KorayKavakli]

Issue #22 resolves the case.

[kaanaksit]

Adding @askaradeniz for visibility, and closing the issue. Thanks @KorayKavakli !