PR: Add Whitespace option in the import wizard

[bcolsen]

This PR fixes #4581 by adding continuous whitespace as an option to the column separator section of the import wizard.

Let me know if this needs a test, and I'll write one.

Currently the data import wizard doesn't play nicely with text data with multiple spaces as delimiters(or maybe I don't play nicely with the data importer ;-). This is common in fixed width data sets like this:

FIRST  LAST           STATE     TELEPHONE      AGE   WEIGHT
John   Smith          WA        418-Y11-4111    26    3.0456
Mary   Hartford       CA        319-Z19-4341     5   13.5687
Evan   Nolan          IL        219-532-c301   145   45.7890

Putting a ' ' (a space) in a the 'other' text box gives this:

When it could give this:

It looks like this:

[ccordoba12]

LGTM, thanks!