enb: add measurement modifier to scenario files

this commit adds basic support for configuring measurements in the
eNB config. It currently support A1, A2, and A3 events.
By default UE measurements are turned off and need to be enabled by
configuring an event with:

+mod-enb-meas-event@{name},{report_type},{value},{hysterisis},{time to trigger}

For example one can update the a2 and a3 event with:

+mod-enb-meas-event@a2,rsrq,-40,2,480+mod-enb-meas-event@a3,rsrp,6,1,512

Change-Id: Ia7657be2396886840570bc41645450a268b4cfff
diff --git a/example/defaults.conf b/example/defaults.conf
index 5cda132..f3994bb 100644
--- a/example/defaults.conf
+++ b/example/defaults.conf
@@ -110,6 +110,19 @@
   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