Add bindings to ASTRA cylindrical detector geometries

[wjp]

This adds bindings for the CylindricalDetector geometry to the astra_cuda tomography backend.

Known bug: there is a misinterpretion of the detector center if the detector partition isn't centered around 0, which is the case for quarter-pixel-shifted detectors. Fixing this needs to be coordinated with the Mayo CT data loader, which currently is assuming the presence of this bug.

[pep8speaks]

Checking new PR...

• In the file odl/tomo/backends/astra_cuda.py:

Line 143:80: E501 line too long (80 > 79 characters) Line 141:80: E501 line too long (80 > 79 characters)

• In the file odl/tomo/backends/astra_setup.py:

Line 768:39: E202 whitespace before '}' Line 766:43: E202 whitespace before '}' Line 417:1: E303 too many blank lines (3) Line 386:80: E501 line too long (81 > 79 characters)