SW-8 Suggest a scheme of 'Mapper'

This pull request fixes the following issues, please read them to understand this implementation better:
- SW-8 Suggest a scheme of 'Mapper'
Proposed solution is available on issue page #11.

- SW-13 Implement additional methods for Reflections.class
You can read more about this implementation on issue page #19

- Other `Reflections` class refactorization.
I have also found these methods helpful but hard to remember:
``` java
createValueIfNull(object, field);
setValue(field, object, value); // very easy to mess up with arguments
getValueField(object, field);
```
I've made them public and redesigned as follows:
``` java
Reflections.onObject(object).createValueIfNull(field); // corresponds createValueIfNull(object, field)
Reflections.onObject(object).setField(field, value); // corresponds setValue(field, object, value);
Reflections.onObject(object).getFieldValue(field); // corresponds getValueField(object, field);
``` 
@lstypka can you share your opinion on those?