Feature/graph manager (#38)

* Initial changes

* Working state

* Working state

* Working state

* Working state

* Working state

* Working state

* Added graph listener

* Updates

* Testing name demangling

* Graph manager: reworked

* Remove debug trace

* Treat errors when freeing rcutils resources

* Improve logics for discovering entities

* Working state: Micro-ROS graph manager

* Fix micro_ros_graph_info typesupport type name

* Remove double CMakeLists comment

* Remove package.xml commented block

* Add missing include

* Added CI

* Remove GUID_t param from callbacks signature

* Add services names and types to micro-ROS graph topic

* Differenciate between service server and clients

* remove debug traces

Co-authored-by: Pablo Garrido <pablogs9@gmail.com>

.github/workflows/ci.yml

@@ -0,0 +1,26 @@
+name: CI micro-ROS Agent
+
+on:
+    pull_request:
+      branches: 
+        - '**'
+
+jobs:
+
+    microros_agent_ci:
+        runs-on: ubuntu-20.04
+        container: ros:foxy
+    
+        steps:
+        - uses: actions/checkout@v2
+          with:
+            path: src/micro_ros_agent
+
+        - name: Download dependencies
+          run: |
+            git clone -b foxy https://github.com/eProsima/Micro-XRCE-DDS-Agent src/microxrcedds_agent
+      
+        - name: Build
+          run:  |
+            . /opt/ros/foxy/setup.sh
+            colcon build