Incorrect signature for Dataset.BuildOverviews in C# bindings

[jbeverage]

The signature for Dataset.BuildOverviews? in the C# bindings is: int BuildOverviews?(string resampling, int overviewlist)

The C++ signature has many more arguments, and it seems like at the very least you have to pass in an array of overview levels instead of just a single int for the overviewlist to have the method do anything meaningful.

[tamas]

The following changes have been made for the SVN trunk:

1. Added the following signature for the Dataset class: public int BuildOverviews?( string resampling, int[] overviewlist)

2. Added apps/GDALOverviews.cs to demonstrate the usage of Dataset.BuildOverviews?

3. Added support for extracting a particular overview int GDALRead.cs and GDALReadDirect.cs.

To test this feature one can use the following commands:

gdaloverviews {GDAL dataset name} {resamplealg} {level1} {level2} ... gdalread {GDAL dataset name} {outfile} {level1} gdalread {GDAL dataset name} {outfile} {level2} ...