Reading a volume

[jcrivenaes]

Currently you have read_subvolume(self, min_il, max_il, min_xl, max_xl, min_z, max_z). That means you have to spesify all start/stop inlines, xlines and zsamples. I propose:

These are defaulted to actual minimum/maximums of inline/xline/samples; so that
read_subvolume() will return numpy for the whole volume.

Alternatively, a read_volume method

[da-wad]

This should do the job. The library wasn't originally intended for cubes which fit uncompressed in memory... but good to have included if it's useful.