[MRG] copy dimensions from non-typecast variable config-space if available

[Sam3077]

• space.dimension is typecast to a Dimension object.
• This means that the copied Optimizer would behave differently since its dimensions are no longer treated as a ConfigurationSpace.
• This change uses the saved, original config_space variable to achieve consistent behavior.
• If config_space is not available, just use the dimensions as previously done.

[bessex]

Looks good!