* create cppcheck and clangformat targets

* apply code style (#67)
* send values by reference
* fix warnings on plugin destruction by disconnecting dataengines first
* fix invalid hddtemp group definition

sources/clang-format.cmake

@@ -0,0 +1,18 @@
+# additional target to perform clang-format run, requires clang-format
+
+# get all project files
+file(GLOB_RECURSE ALL_SOURCE_FILES *.cpp *.h)
+foreach (SOURCE_FILE ${ALL_SOURCE_FILES})
+    string(FIND ${SOURCE_FILE} ${PROJECT_TRDPARTY_DIR} PROJECT_TRDPARTY_DIR_FOUND)
+    if (NOT ${PROJECT_TRDPARTY_DIR_FOUND} EQUAL -1)
+        list(REMOVE_ITEM ALL_SOURCE_FILES ${SOURCE_FILE})
+    endif ()
+endforeach ()
+
+add_custom_target(
+        clangformat
+        COMMAND ${CLANGFORMAT_EXECUTABLE}
+        -style=file
+        -i
+        ${ALL_SOURCE_FILES}
+)