Added Pair Plot Options sub dialog for Legend on Graphs dialog

[MeSophie]

Fixes #7212
@rdstern I added legend on Graphs dialog for Pairs radio button.
@N-thony Please can you have a look.

[rdstern]

@MeSophie the Options button On Describe > Two/Three Variables > Graph > Pairs is still disabled. So I have not been able to check.

[N-thony]

@MeSophie the Options button On Describe > Two/Three Variables > Graph > Pairs is still disabled. So I have not been able to check.

@rdstern I checked this and it seems to work fine

@MeSophie I noticed now we lost the Plot Options button for the By option, but Pair Plot Option seems to work fine

[N-thony]

@anastasia-mbithe can you peer-review this?

[MeSophie]

@rdstern the Plot Options is visible for By now.

[rdstern]

@MeSophie this is already looking nice.
a) I noticed that Ok is only enabled when you include the Colour (Optional). It should be included as soon as the pairs can be used. Possibly the Options button should only be enabled when the colour is completed?
b) Do we need 2 controls in the sub-dialogue? I am happy with that, but perhaps Legend could be just a label, with None as the default? I am happy either way though.

[MeSophie]

@MeSophie this is already looking nice. a) I noticed that Ok is only enabled when you include the Colour (Optional). It should be included as soon as the pairs can be used. Possibly the Options button should only be enabled when the colour is completed? b) Do we need 2 controls in the sub-dialogue? I am happy with that, but perhaps Legend could be just a label, with None as the default? I am happy either way though.

@rdstern The OK is only enabled when you include the Colour (Optional) because if you don't include it and use legend you will have the following error.

And For the two controls in the sub-dialog the first one can be enough the second one is just for cosmetic to let the user put the legend wherever he want.

[rdstern]

@MeSophie but that's why I would strongly prefer you (instead) activate Ok without needing to add the optional factor. But disable the Options, or the legend instead!

Ok with the 2 controls. But I assume now (with your options) you could tick the first one to have a legend, and then set it to none? That's odd.

[N-thony]

@MeSophie but that's why I would strongly prefer you (instead) activate Ok without needing to add the optional factor. But disable the Options, or the legend instead!

Ok with the 2 controls. But I assume now (with your options) you could tick the first one to have a legend, and then set it to none? That's odd.

@MeSophie any progress?

[MeSophie]

but that's why I would strongly prefer you (instead) activate Ok without needing to add the optional factor. But disable the Options, or the legend instead!

@rdstern according to @N-thony comment I think the dialog and sub-dialog are better now. I remove the first check box on sub dialog and made Pairs Plot Option sub dialog enable when we fill the Colour Factor.

[rdstern]

@MeSophie looks good. Thanks. I am approving

[lloyddewit]

@MeSophie thanks, looks good, just a couple of questions

[MeSophie]

@MeSophie thanks, looks good, just a couple of questions

@lloyddewit I revolved your comments thank you.

[rdstern]

@lloyddewit I am not sure what should happen if I click on revert above?

I would like to reopen this pull request, or issue, by @MeSophie . This is for the following reasons.
a) In Version 0.7.16 the Pairs Plot Options is disabled. I thought this was the purpose of this pull request.
b) Our main plotting features have regressed again in a small way, and I wonder if this issue/pull request is related. Namely a useful option in the plotting sub-dialogue is shown here:

The default option here used to be None - so to be able to not have a legend. This has disappeared! I don't know if this is related to this pull request, or not?

[lloyddewit]

I am not sure what should happen if I click on revert above?

@rdstern This would create a new PR with proposed changes that would undo the specific changes in this PR.
We don't know for certain what caused the regression. So a full revert may not be the best option. I suggest that we start with the latest master version and investigate the bug. I assume that @MeSophie is the best person for this.

[MeSophie]

@MeSophie I investigate on this and my question is Do you need the Pairs Plot Options is disabled or enable? because from now it is enable only when you fill the colour receiver.