retcode field in DiffEqArray

[ivborissov]

As discussed in Slack. DiffEqArray is a convenient way to reduce Solution type and wrap (u,t) results, it seems reasonable to add optional retcode field to DiffEqArray. What do you think? My current setup is: I run ensemble simulations and reduce each simulation to a DiffEqArray storing just (u,t) . Some parameters sets may result in Unstable retcode or Terminated if some termination criteria is present. To filter such simulations I define a solution type like

struct MySol
 sol::DiffEqArray
 retcode::Symbol
end

to save both solution and it's retcode