Created metric class

Metric collects updates from sensor. Report displays metric readings
depending on reportingType.

Tested:
  - Added new units tests for Metric class
  - All other unit tests are passing

Change-Id: I19f4831fab163a4f9540cef7bb23e903ae90fddf
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/src/report_manager.cpp b/src/report_manager.cpp
index d23b589..eb2d767 100644
--- a/src/report_manager.cpp
+++ b/src/report_manager.cpp
@@ -16,6 +16,7 @@
     reportStorage(std::move(reportStorageIn)), objServer(objServerIn)
 {
     reports.reserve(maxReports);
+
     loadFromPersistent();
 
     reportManagerIface = objServer->add_unique_interface(