[WIP] Remove static function WarpX::RefRatio

[lucafedeli88]

This PR removes the following static function from the WarpX class:

IntVect
WarpX::RefRatio (int lev)
{
    return GetInstance().refRatio(lev);
}

Most of the other changes are needed to pass the refinement ratios down to the functions that need this information. Few additional changes concern other parameters that are now passed together with the refinement ratios and which were before obtained via static methods of the warpx class.