Failure to run some examples due to both Plots and ReachabilityAnalysis exporting "center"

[hurak]

I am not sure if the following qualifies as an issue, but it certainly prevents some examples from the webpage from running successfully just by running the copy-pasting their code: for example, the one from https://juliareach.github.io/ReachabilityAnalysis.jl/dev/tutorials/linear_methods/discrete_time/.

Namely, both Plots and ReachabilityAnalysis export "center". As a result, the following code

using ReachabilityAnalysis, Plots
X0 = BallInf(ones(2), 0.2)
plot(X0, c=:white)
c = center(X0) 

returns the error

ERROR: UndefVarError: `center` not defined

As a result the example code on the above linked webpage cannot be run without adding the full qualification:

c = ReachabilityAnalysis.center(X0)

but this should better be included in the example code directly.

Unless there is a neater solution.

[mforets]

i think this is a known issue; Plots exports a method called center (why?!) and so does LazySets.

... and ReachabilityAnalysis just reexports LazySets names for convenience.

[mforets]

looking at the code i see that we are hiding the relevant line https://github.com/JuliaReach/ReachabilityAnalysis.jl/blob/master/docs/src/tutorials/linear_methods/discrete_time.md

using ReachabilityAnalysis # hide
using ReachabilityAnalysis: center  # hide

but showing them seems better, to avoid confusion.

[mforets]

being done in #752