Created sensor cache class

Created sensor cache and sensor interface that needs to be
implemented by sensors.

Tested:
- Sensors created by sensor cache are stored and reused if
  there is try to access same sensor multiple times.
- All other units tests are passing

Change-Id: I552b2016bca4688e1b2a223297587826af256b54
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/tests/src/utils/generate_unique_mock_id.cpp b/tests/src/utils/generate_unique_mock_id.cpp
new file mode 100644
index 0000000..f3e3f01
--- /dev/null
+++ b/tests/src/utils/generate_unique_mock_id.cpp
@@ -0,0 +1,7 @@
+#include "generate_unique_mock_id.hpp"
+
+uint64_t generateUniqueMockId()
+{
+    static uint64_t id = 0u;
+    return id++;
+}