Simplify REMIND Calibration Data Transfer

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

The split between CES parameters in the .inc file and the .gdx file is a left-over from the development time of the CES calibration.
We could cut down on complexity and possible sources of error by simply dropping the .inc files, as the CES parameters should not be changed in between. (Currently there is a bug concerning this: #1544). We could also augment the gdxes by some calibration information like

Scalar
  s_calibration_info   "this run was calibrated on yyyy-mm-dd to input data revision …"
;

[LaviniaBaumstark]

sounds good to harmonize the process of reading data for the calibration. I alos like the idea of havin the info on which input data the calibration was based on