Removed module SUFR_angles_periodic

* Removed module SUFR_angles_periodic:
  * moved contents to module SUFR_angles
Removed module SUFR_date_and_time_JD

* Removed module SUFR_date_and_time_JD:
  * moved contents to module SUFR_date_and_time
Removed obsolete functions

* Removed obsolete functions:
  * compute_median()     -  use median() instead
  * compute_median_sp()  -  use median_sp() instead
  * compute_stdev()      -  use stdev() instead
  * compute_stdev_sp()   -  use stdev_sp() instead