Implemented sensor class

Sensor class was introduced, it monitors
xyz.openbmc_project.Sensor.Value, for change and notifies all
listeners.

Tested:
  - Unit tested with service stub that provides dbus interface
    xyz.openbmc_project.Sensor.Value
  - All changes are delivered to listeners
  - All other unit tests are passing

Change-Id: I8c9d58cc986c1fe2a4d2386815d559814016efa6
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/tests/meson.build b/tests/meson.build
index 08a6e6c..89e5088 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -6,8 +6,7 @@
         gtest_dep = declare_dependency(
             dependencies: [
                 dependency('threads'),
-                gtest_proj.dependency('gtest'),
-                gtest_proj.dependency('gtest_main'),
+                gtest_proj.dependency('gtest')
             ]
         )
         gmock_dep = gtest_proj.dependency('gmock')
@@ -27,9 +26,16 @@
             '../src/persistent_json_storage.cpp',
             '../src/report.cpp',
             '../src/report_manager.cpp',
+            '../src/sensor.cpp',
             '../src/sensor_cache.cpp',
+            'src/dbus_environment.cpp',
+            'src/main.cpp',
+            'src/stubs/dbus_sensor_object.cpp',
+            'src/test_detached_timer.cpp',
             'src/test_persistent_json_storage.cpp',
+            'src/test_sensor.cpp',
             'src/test_sensor_cache.cpp',
+            'src/test_unique_call.cpp',
             'src/utils/generate_unique_mock_id.cpp',
         ],
         dependencies: [