add unit tests and *Data methods rebuild (issue #7, issue #51)

This version introduces multiple enhancements:

after merge change some getData methods to toArray and changed methods name in example file
added test for create object with json data and some useful methods to test creation with different data types

Details of additions/deletions below:
--------------------------------------------------------------

Modified:   Test/ObjectTest.php
            -- Added --
                testCreationWithJsonData allow to create object with given json string
                _exampleJsonData create json data to test
                _exampleSimpleXmlData create simple xml data to test
                _exampleXmlData create xml data to test
                _exampleSerializedData create serialized string to test
                _exampleStdData create std object to test
            -- Updated --
                testGetDataFromObject getData changed to toArray
                testFullDataRestoration getData changed to toArray
                testDataPreparationOnEnter getData changed to toArray
                testDataPreparationOnReturn getData changed to toArray

Modified:   Base/BlueObject.php
            -- Updated --
                toXml getData changed to toArray
                toStdClass getData changed to toArray

Modified:   examples/base_object/replace_data.php
            -- Updated --
                hasDataChanged changed to dataChanged