Match directory structure with polygon package

[eldering]

Since it seems that not all information (e.g. problem statements) can be extracted from polygon using the API, I would suggest to try to match the directory structure that polygon package files use. Then one can more easily combine using both.

For example, I would suggest to write test files using '%02d' since that matches the names exported in the polygon package files. Further, rename the directory 'src' to 'files' and move 'check.cpp' there.

Then again, I don't know how stable the polygon package format is.

[kunyavskiy]

To be honest, the format is close to one i use for developing problems without polygon.

Seems it's better to make this configurable. I should be able to configure directories for all types of files. But I still don't understand how to make config better/