--cols-file in fits importer

[gregreen]

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This pull request adds the ability to specify --cols-file with lsd-import fits. It also fixes a bug that used to occur when a database column name was not recognized.

I had to convert tabs to spaces in order to edit this file, because my text editor wouldn't allow me to write tabs, so that complicates reading the diff.

[mjuric]

I hate to ask this, but for consistency with the rest of the codebase (and to make the diff more readable) could you switch spaces back to tabs? There's a unix command unexpand (run man unexpand) that should "just work (tm)".

PS: Which editor do you use?

[gregreen]

I use vim. It's kind of a pain to switch it to use tabs.

As I'm making changes to the code base, I'm using expand to replace tabs with spaces. I'd hate to go back - spaces display the same everywhere.

[gregreen]

I've been trying to make the diffs more readable by doing expand and committing, before making any further changes. I didn't think to do that here.