YAML as a drop-in replacement for libconfig

This commit introduces a substitute module library for setting up softmodems using YAML instead of libconfig.
The softmodems should work the same with both types of files. Extra care was put to make sure the behavior
of both modules is the same.

Example yaml config files were added for the UE and gNB

ci-scripts/conf_files/nrue.uicc.yaml

@@ -0,0 +1,28 @@
+uicc0:
+  imsi: 208990100001100
+  key: fec86ba6eb707ed08905757b1bb44b8f
+  opc: C42449363BBAD02B66D16BC975D77CC1
+  dnn: oai
+  nssai_sst: 1
+
+#/* configuration for channel modelisation */
+#/* To be included in main config file when */
+#/* channel modelisation is used (rfsimulator with chanmod options enabled) */
+channelmod:
+  max_chan: 10;
+  modellist: modellist_rfsimu_1
+  modellist_rfsimu_1:
+    - model_name: rfsimu_channel_enB0
+      type: AWGN
+      ploss_dB: 20
+      noise_power_dB: -4
+      forgetfact: 0
+      offset: 0
+      ds_tdl: 0
+    - model_name: rfsimu_channel_ue0
+      type: AWGN
+      ploss_dB: 20
+      nose_power_dB: -2
+      forgetfact: 0
+      offset: 0
+      ds_tdl: 0