Put X field above Y field in Delimited Text dialog. Fix #11746.

[ismailsunni]

Description

Address this ticket https://issues.qgis.org/issues/17746
Before (from the ticket):

After:

Checklist

Reviewing is a process done by project maintainers, mostly on a volunteer basis. We try to keep the overhead as small as possible and appreciate if you help us to do so by completing the following items. Feel free to ask in a comment if you have troubles with any of them.

• Commit messages are descriptive and explain the rationale for changes
• Commits which fix bugs include fixes #11111 in the commit message next to the description
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• I have read the QGIS Coding Standards and this PR complies with them
• This PR passes all existing unit tests (test results will be reported by travis-ci after opening this PR)
• New unit tests have been added for core changes
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Funded by: Kartoza

[m-kuhn]

Good improvement, thanks 👍