Update write_solution method so it writes from Unit Operations directly instead of using ida.ouput

[daklauss]

As for now the solution recorder initializes with creating a dictionary-array structure that resembles the the state structure, so it is possible to iterate over the the solution output of ida(s). It may be better to write the solution from the saved state of the unit operation after ida calculated each y instead of after ida calculated each section.

Possible advantages:

• coupling of calculated state?
• no need of initializing the solution structure
  Open questions:
• When to write the solution?
  • IDA may calculate more steps than our given time resolution depending on stifness
  • can't write everytime _compute_residual is called or have to filter much?
• Consider using step instead of solve to iterate ourself over the give time resolution