Introduce doc/examples/ directory

It contains simple usual setups to get started with osmo-gsm-tester,
such as creating a 4G network using srsLTE or a 2G network using the
osmocom stack (+ ofono modems).

Change-Id: I55d5b1152da201799af21a77ef6c562f97bd94fc
diff --git a/doc/examples/4g_srsLTE/defaults.conf b/doc/examples/4g_srsLTE/defaults.conf
new file mode 100644
index 0000000..4a3b4c4
--- /dev/null
+++ b/doc/examples/4g_srsLTE/defaults.conf
@@ -0,0 +1,40 @@
+epc:
+  type: srsepc
+  mcc: 901
+  mnc: 70
+  qci: 9
+
+srsepc:
+  enable_pcap: false
+
+enb:
+  mcc: 901
+  mnc: 70
+  transmission_mode: 1
+  num_cells: 1
+  enable_measurements: false
+  a1_report_type: rsrp
+  a1_report_value: -105
+  a1_hysteresis: 0
+  a1_time_to_trigger: 640
+  a2_report_type: rsrp
+  a2_report_value: -110
+  a2_hysteresis: 0
+  a2_time_to_trigger: 640
+  a3_report_type: rsrp
+  a3_report_value: 6
+  a3_hysteresis: 0
+  a3_time_to_trigger: 480
+
+srsenb:
+  num_prb: 100
+  enable_pcap: false
+
+srsue:
+  enable_pcap: false
+  airplane_t_on_ms: -1
+  airplane_t_off_ms: -1
+  num_carriers: 1
+
+iperf3cli:
+  time: 60