Plugin refactored to use promises

Promises used instead of callback "hell" preffered by node.js.

Changes are only internal so tasks should work as before.
However, this probably should be version 0.2.0 - things will not work if other software utilizes individual components.

Some other changes includes:
- node-expat xml parser for config.xml - it's faster
- added TizenConfig.configParsed.content property