[testHatoholArmPluginInterface] Add a new test: test_appendItemInt().
[testHatoholArmPluginInterface] Add a new test: test_appendItemUint64().
[HatoholArmPluginInterface] Fix a problem that casts ItemUint64 to int.

This conversion will fail.
[testHatoholArmPluginInterface] Make a helper function.
[testHatoholArmPluginInterface] Clean up.
[testHatoholArmPluginInterface] Clean up.
[testHatoholArmPluginInterface] Fix a bug that takes test data as int.
[DataSamples] Clean up.
[testDBTermCodec] Clean up.
[DataSamples] Add files we mistakenly forgot to add.
[testHatoholArmPluginInterface] Use the template parameters name that is the same as others.
[HatoholArmPluginInterface] Fix a bug that doesn't put a double value.
[test_appendItemDouble] Add a new test: test_appendItemString().
[test_appendItemDouble] Remove a wrong comment.
[DataSamples] Fix an empty sample that was set mistakenly.
[HatoholArmPluginInterface] Add a new method: createItemData().
[HatoholArmPluginInterface] Use a defined constant.
[testHatoholArmPluginInterface] Add a new test: test_appendItemDataWithNull().
[HatoholArmPluginInterface] Add an explaination of the method.
[HatoholArmPluginInterface] Add an explaination of the method.