Remove GDAL dependency

[niniemann]

While compiling gdal with geos support (once again), I have some time to think about this process. And why we actually need it.

The answer is: We don't.

What do we need?

• Geometry types
• Geometry operations
• Geometry to WKT/WKB would be nice
• Coordinate system transformations

"GDAL with GEOS support" uses:

• GEOS
• libproj4

What does GEOS provide?

• Geometry types
• Geometry operations
• Geometry to/from WKT/WKB (e.g. geos::io::WKTReader)

What does libproj4 provide?

• Coordinate system transformations

So why the hell am I compiling libproj4 and geos into gdal instead of using them directly? I guess because I couldn't find the WKT/WKB import/export of GEOS at first. Well, but it is there. And removing the dependency to a custom-compiled GDAL would make sempr much more appealing. ;)

The only question is: Is there anything in GDAL that could be useful later on? What is its benefit? As far as I can see it "only" adds support for a whole bunch of vector- and gridmap formats, as well as some database stuff? I don't think that we really need that.

[niniemann]

the dependency to GDAL has been removed.