fix gh-1461
pep8
Add comment to tell to don't use the old neighbourhoods.py version and point to the new ones.

Also make sure the input is on the CPU, so a transfer is added when needed.
Implement GpuImages2Neibs mode ignore_border.
Don't try to move to the GPU alloc that aren't float32.

This is needed to make the new GpuImages2Neibs ignore_border mode pass.
Merge pull request #1466 from nouiz/gh1461

Gh1461