Renaming

* solvers -> solver
* adaptive_functions -> adaptive_function
* callbacks -> callback
* operators -> operator
* pinns -> physics_informed_solver
* layers -> block

pina/problem/zoo/poisson_2d_square.py

@@ -1,7 +1,7 @@
 """ Definition of the Poisson problem on a square domain."""
 
 from pina.problem import SpatialProblem
-from pina.operators import laplacian
+from pina.operator import laplacian
 from pina import Condition
 from pina.domain import CartesianDomain
 from pina.equation.equation import Equation