update ggplot scatterplot tool

[hechth]

FOR CONTRIBUTOR:

• I have read the CONTRIBUTING.md document and this tool is appropriate for the tools-iuc repo.
• License permits unrestricted use (educational + commercial)
• This PR updates an existing tool or tool collection

Closes #6692

[hechth]

@bgruening ready for review

[bgruening]

@hechth can you please test in planemo what happens when you provide a file without a header? How does the UI react?

[hechth]

Well it just will always think there is a header ... so it treats the first line as a header.

[hechth]

@bgruening I added a select to choose whether there is a header or not

[bernt-matthias]

In hindsight I wish I would not have implemented galaxyproject/galaxy@2395e65.

An.extra tool that just adds metadata to a tabular file would have been better. Maybe such a tool would even be possible without duplicating the dataset.

Then you could just rely on the metadata here (and no conditional would be needed) and the user could use the additional tool to set the metadata of needed.

[bgruening]

@bernt-matthias I'm not sure I have followed all the tabular discussions. Do you think we can merge this PR or not?