vcs should rember the original value stored by the user

[doutriaux1]

example

>>> gm  = x.createisoline()
>>> gm.line= ['dot','dash']
>>> gm.line
['dot', 'dash']
>>> gm.line= [1,2,3]
>>> gm.line
['dash', 'dot', 'dash-dot']
>>> 

[danlipsa]

@doutriaux1 This case is not too bad as there is a one-to-one mapping between numbers and line type descriptions, isn't it?

[danlipsa]

Also look at
datawc_ being changed to cdtime.reltime for time axis. See
#2007

[doutriaux1]

@danlipsa yes #2007 is the most disturbing, but we might as well fix it everywhere so it consistently return to the user what the user stored.

[doutriaux1]

migrated