rename files if copied in session as reference and correlate

[paskino]

closes #184

[lauramurgatroyd]

I found this does not work for tiffs - I get the following error:

And on the command line it gives an error: "When reading multiple files, all files must TIFF formatted."

I believe what is happening is it copies every tiff file to have the same new name, so they all overwrite each other.

[paskino]

I think I fixed the behaviour, but see also #193

[lauramurgatroyd]

I encountered a couple of issues:

• When I encountered an error when clicking "Visualise" [I think the error was due to trying to downsample a compressed .mha file? ] I had the error message pop up, but the progress dialog remained in place.

• Issues with .mhd files, as the .mha created is compressed so can't be read by the resample reader. [ see comment ]

[lauramurgatroyd]

Just fixed this issue:

When I encountered an error when clicking "Visualise" [I think the error was due to trying to downsample a compressed .mha file? ] I had the error message pop up, but the progress dialog remained in place.