add the time as a string

AircraftReport.proto

@@ -10,5 +10,5 @@ message AircraftReport {
     Coordinate position           = 3; // current WGS84 position
     Dynamics   dynamics           = 4; // current aircraft dynamics
     string     destination        = 5; // the destination airport
-    Time       timeAtIAF          = 6; // UTC time when aircraft is at IAF
+    string     timeAtIAF          = 6; // UTC time when aircraft is at IAF
 }

AircraftSchedule.proto

@@ -8,5 +8,5 @@ message AircraftSchedule {
     Aircraft aircraft       = 1; // aircraft information
     string   arrivalRoute   = 2; // planned arrival route
     string   arrivalRunway  = 3; // planned arrival runway
-    Time     reachIafAtTime = 4; // UTC time when the aircraft needs to pass IAF
+    string   reachIafAtTime = 4; // UTC time when the aircraft needs to pass IAF
 }

BaseTypes.proto

@@ -11,8 +11,3 @@ message Dynamics {
     int32 altitude      = 2; // given in feet
     int32 verticalSpeed = 3; // given in feet/min
 }
-
-message Time {
-    int32 hour   = 1; // hours in 24-format
-    int32 minute = 2; // minutes
-}