* Remove MIMO_mode_indicator: it is simply not used ATM
* Remove min_rb_unit as parameter: function auto-detects
* Remove commented code
* Remove slice sharing/multiplexing: it is broken
* Remove UE sorting, add UE with add_new_ue() in MAC
  - UE sorting is useless overhead on every iteration, instead it should
    be governed by a scheduling algorithm (e.g., RR or PF)
  - The MAC keeps a UE list and automatically adds a UE
  - UE_list empty, set head to -1
* Remove slice_positioning: the slicing functionality is broken
* Remove unused/untested code