Change the default visibility of the color bar to true

[stefanhahmann]

By chance I recently found out that a feature that I was always missing does actually exist: a legend for the Grapher views

Since, I think this feature is so super important and perhaps I am not the only one for whom it is too well hidden how to activate it (it is actually not hidden at all, but Mastodon has grown so powerful with so many options that for newbees, it might be hard to find the relevant stuff), I would like to suggest to change the default such that it is activated, which is done in this PR.

[tinevez]

I intead appreciate if the scale bar would be off by default...

[stefanhahmann]

I intead appreciate if the scale bar would be off by default...

First of all: apologies, for insisting so much on this..

Since I was so convinced of the usefulness of this feature (maybe its due to fact of my former life as a cartographer, in which I was always forced to put legends into maps to explain what the colors in the maps mean), I discussed this with some users (Mette, Michalis, @xulman, Johannes) in the recent weeks. I have to admit that I may have biased them with my strong opinion on this, but their average feedback was also that they did not even knew about this feature and what rather prefer it being switched on by default than off.
In case they would not need it, they would start looking for an option to switch it off. On the other side not knowing that this feature exists, they would not have searched for it even though they find it useful.