[xwalkdriver] Refactor platform-related code of Android and Tizen

1.Abstract DeviceBridge class (device bridge tools api) for adb or sdb.
2.Implement SdbImpl class to manipulate Tizen sdb tools.
3.Implement specific target device class deriverd from Device abstraction.
4.Update binary xwalkdriver64_20141222
Merge pull request #8 from wuyuehang/webdriver_refact

[xwalkdriver] Refactor platform-related code of Android and Tizen