rasterlite as mapnik input plugin

[kunitoki]

I've added an initial draft of the RasterLite input plugin for mapnik.
This way we can draw rasters in sqlite databases with good performance
gain over geotiffs. With the actual state of mapnik2, we have full
support for Spatialite and Rasterlite enabled database (you can use
them seamlessly to draw your favourite maps).

Here is the changeset (the code is actually only in SVN, in the
mapnik2 branch):

http://trac.mapnik.org/changeset/1480

Hope someone find this useful !

Cheers

Lucio Asnaghi