Exporting of maps with rasters

[ivanprado]

At this moment, importing/exporting of maps that includes rasters don't work. (Probably because overviews are not exported and because is failing for some reason when there is a raster). Solve it so that import/export of maps with rasters works.

There is an old ticket talking about that here: #60 that was closed as it was talking about keeping original raster tif file.