[processing] improve graphs

[alexbruy]

Use Plotly to generate interactive graphs (zooming, selecting, panning etc).

[ghtmtt]

are you serious?! We can use plotly to make plot within Processing?! This is AWESOME!
Anyway, I cannot see the plots in the toolbox yet.. Is the package plotly automatically installed?
Thanks Alex!

[luipir]

@ghtmtt you need plotly python module installed... and them thi PR will substitute the matplotlib plot engine that was used before in the graph result window

[ghtmtt]

@luipir ah ok I see... So the user has to install plotly by him self right? Will the package be in the default installation in the future (so like numpy)?
Thanks Luigi and Alex!

[ghtmtt]

@luipir @alexbruy as I said, this is really a great PR! In Girona, together with @mdouchin we tried to make a plugin using Plotly.
However, IMHO, if the user has to install by himself plotly via pip then the users that will discover the plots drop down.
So the question is, is in planned to put plotly package directly in the source code (so like the other current python external packages)?

Thanks again for this Alex!

[luipir]

@ghtmtt this is a packaging problem more than a coding problem... plotly can be added as was added matplotlib. I can't find limitation to add plotly as new dependecy

[ghtmtt]

thanks @luipir for clarifying.. So there are plans to add plotly as default dependency right?
Thanks again

[jef-n]

done in a217181 - and included in OSGeo4W

[alexbruy]

Just to clarify, plotly is not a hard requirement. Processing will work without it too, as it did when matplotlib was used.

[ghtmtt]

@jef-n thanks for this!
@alexbruy yes it works also without plotly but it's a pity not using it ;) thanks again for the work!