vcs window do not disappear

[doutriaux1]

At least on mac

import vcs
x=vcs.init()
x.plot(s,"default","isoline","default")
x.png("iso")
x=vcs.init()
x.plot(s,"default","isofill","default")

Leaves unaccessible window opened, as shown in png bellow:

[danlipsa]

@doutriaux1 This should have two windows because you called init twice and never close, isn't it?

[doutriaux1]

@danlipsa no because I have the x=vcs.init() twice, so essentially the first x object is gone.
And indeed I can't access that window anymore.
Actually the follwoing is an even better example

import vcs
x=vcs.init()
x.plot([1,2,3])
del(x)

window hangs but is not reachable.

[doutriaux1]

i think we need to implement the __del__ function correctly. It's probably related to the soft-links issue that @dlonie pointed out a long time ago.

[durack1]

@doutriaux1 @danlipsa I believe this issue is almost a dupe of #86 the behaviours that @doutriaux1 is explaining is eerily similar