Better handling of titles in plotly

[OriolAbril]

AFAIK, plotly doesn't have a constrained_layout=True that can easily fix the issue on the user side, so we should look into handling titles a bit better so they don't overlap so much with the upper subplot (if there is one). A quick look at the example gallery shows this quite clearly.

I think plotly reserves this space at plot creation time, so a potential workaround would be to add titles to the plots when they are created, then update them so they show an empty string yet hopefully keeping the grid spacing with space for the title to potentially be filled later by the plotting functions.