Move guassopt to optics/guassopt

This is a PR to move ```sympy.physics.guassopt``` to ```sympy.physics.optics.guassopt```.
I'm getting a code quality error here.
```
AssertionError: File contains an implicit import: sympy/sympy/physics/optics/__init__.py, line 19.
```
Same procedure of import works in vector module(I am following that). @srjoglekar246 Please help.