BaseRobyn file_path and other parameters

[dave42w]

          we probably also don't need a file_path in the subrouters now, right?

Originally posted by @sansyrox in #1100 (comment)

Agreed.

It seems to me that the SubRouter should not hold any of the general configuration (config object, filepath etc). Instead it needs to know the BaseRobyn that it belongs to (to get the config etc from). So include_router should set a ParentBaseRobyn property in the SubRouter that is being included.

[sansyrox]

Yep, agreed. This will also likely be a breaking change.

[dave42w]

Yep, agreed. This will also likely be a breaking change.

Hopefully, we can keep that to a minimum at least for the documented ways of using Robyn.

I'll do it in small careful steps as usual.