GetSubDatasets() sugar missing in NG python bindings

[warmerdam]

The old generation bindings had a "syntactic sugar" method on GDALDataset like this:

    def GetSubDatasets(self):
        sd_list = []
        
        sd = self.GetMetadata('SUBDATASETS')
        if sd is None:
            return sd_list

        i = 1
        while sd.has_key('SUBDATASET_'+str(i)+'_NAME'):
            sd_list.append( ( sd['SUBDATASET_'+str(i)+'_NAME'],
                              sd['SUBDATASET_'+str(i)+'_DESC'] ) )
            i = i + 1
        return sd_list

This was not ported to the NG bindings. I'll do so...

[warmerdam]

This has been introduced into the NG bindings in trunk (r13769) and 1.5 branch (r13770).

It was tested interactively once, but there are no tests for this method in the test suite.