Cleaned the Output symbolic class.
Fixed a bug in SymbolicIndexList
fixed export-to-c example
Tunneling of OnlineData to the CGT
Cleaning export of ACADO function
Tunneling of OnlineData structure in progress:

- Had to heavily mod model_data since there were fcn overloading
  problems.
Part of the CGT example does not work:

- @rienq please take a look at this. I left some comments in the
  example' source.