Add capnp python examples

samples/python/capnp/README.md

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+## Capnp Publisher and Subscriber Example
+
+Minimal Publisher - publishes an example Imu message
+`python3 pub.py`
+
+Minimal Subscriber - subscribes to the Imu message
+`python3 sub.py`
+
+Capnp Message Struct
+
+```
+struct Imu { 
+ timestamp @0: Int64; 
+ accel @1: List(Float32);
+ gyro  @2: List(Float32);  
+}
+```
+
+

samples/python/capnp/messages.capnp

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+@0xb6249c5df1f7e512; 
+
+struct Imu { 
+ timestamp @0: Int64; 
+ accel @1: List(Float32);
+ gyro  @2: List(Float32);  
+}
+

samples/python/capnp/pub.py

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+import sys
+import time
+import capnp
+import random
+import time
+import messages_capnp as msgs
+import ecal.core.core as ecal_core
+from ecal.core.publisher import StringPublisher, MessagePublisher, CapnPublisher
+
+if __name__ == "__main__":
+  ecal_core.initialize(sys.argv, "CapnProto Message Publisher")
+
+  # Create a CapnProto Publisher that publishes on the topic "sensor_imu"
+  pub = CapnPublisher("sensor_imu", msgs.Imu)
+
+  # Infinite loop (using ecal_core.ok() will enable us to gracefully shutdown
+  # the process from another application)
+  while ecal_core.ok():
+    # Create a capnproto Imu message, populate it with random values and publish it to the topic 
+    imu_msg = msgs.Imu.new_message()
+    imu_msg.timestamp = time.monotonic_ns()
+    imu_msg.accel = [round(random.uniform(2.0, 20.0), 2), round(random.uniform(2.0, 20.0), 2), round(random.uniform(2.0, 20.0), 2)]
+    imu_msg.gyro  = [round(random.uniform(0.0, 4.3), 2), round(random.uniform(0.0, 4.3), 2), round(random.uniform(0.0, 4.3), 2)]
+
+    print("Sending: {}".format(imu_msg))
+    pub.send(imu_msg)
+
+    # Sleep 500 ms 
+    time.sleep(0.5)
+
+  # finalize eCAL API
+  ecal_core.finalize()

samples/python/capnp/sub.py

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+import sys
+import time
+import capnp
+import messages_capnp as msgs
+import ecal.core.core as ecal_core
+from ecal.core.subscriber import  MessageSubscriber, CapnSubscriber
+
+# callback function for the subscriber 
+def callback(topic_name, msg, time):
+  # print the received message 
+  print(msg) 
+
+if __name__ == "__main__":
+  # Initialize eCAL
+  ecal_core.initialize(sys.argv, "CapnProto Message Subscriber")
+
+  # Create a subscriber that listenes on the "sensor_imu" topic
+  sub = CapnSubscriber("sensor_imu", msgs.Imu)
+
+  # Set the callback
+  sub.set_callback(callback)
+
+  # infinite loop that keeps the script alive 
+  while ecal_core.ok():
+    time.sleep(0.5)
+
+  # finalize eCAL API
+  ecal_core.finalize()