Image::Stride::sanitise() fix

Fix the case where a limited constraint on the image strides has been provided, and the remaining strides are to be determined based on a reference image.
This was otherwise causing an error when using Image::Stride::contiguous_along_axis(3) if the template InfoType had been expanded from 3D to 4D (and hence stride[3]=0).
Fixes #142.
Image::Stride: further fix to sanitise() and contiguous_along_axis()
small app 'test_strides' to check Image::Stride::get_nearest_match()
Strides::sanitise(): minor changes to argument names & doc
Remove test_strides test app
Merge pull request #144 from jdtournier/stride_sanitise_fix

Stride sanitise fix