Update IPYNB notebooks

[ezgioz]

There is one error to be solved and some points to be updated:

• Error: Notebook validation failed
  Each time I open a IPYNB file, I have the following error:

n invalid notebook may not function properly. The validation error was:
Notebook validation failed: Additional properties are not allowed ('source' was unexpected):
{
"data": {
"image/png": >"iVBORw0KGgoAAAANSUhEUgAAAkwAAAHHCAYAAABN+wdFAAAABHNCSVQICAgIfAhkiAAAAAlw>SFlzAAAPYQAAD2EBqD+naQAAIABJREFUeJzs3XdUFOf+BvBnF1iWjkgvgmLBgoAFRMWSYDA .....

• To be updated
  In one of the files, solution of the model is called "dr" --> It should be "sol" instead, and call "sol.dr" for the decision rule.
  Example:

@time dr_gdp = Dolo.time_iteration(model, verbose=false, maxit=10000);
df_gdp = Dolo.tabulate(model, dr_gdp, :k; n_steps=50)

instead of

@time sol_gdp = Dolo.time_iteration(model, verbose=false, maxit=10000);
df_gdp = Dolo.tabulate(model, sol_gdp.dr, :k; n_steps=50)

Pablo's comment: Maybe we could create a new method for tabulate function to accept "sol" and extract "sol.dr" in the function.

Example:

@time sol_gdp = Dolo.time_iteration(model, verbose=false, maxit=10000);

Then calling

df_gdp = Dolo.tabulate(model, sol_gdp, :k; n_steps=50)

will yield to same output as

df_gdp = Dolo.tabulate(model, sol_gdp.dr, :k; n_steps=50)

• To be updated
  In some julia files such as "RBCS/test_algos.jl", methods are not up to date. Calling "details = yes" for example, returning an error.

[albop]

Thank you @ezgioz for filing this issue.
Regarding the effects of removing details=true (it has been removed as an option), I think the notebooks should use the solution object as it has some pedagogic value, like showing the algo has actually converged.
This doesn't prevent to have compatibility methods to accept a solution object as initial guess. This should probably be an issue on the Dolo.jl repo though.
IMHO, test_algos.jl has nothing to do there. It could just be removed.