VariableCondition symbol is deserialized incorrectly

[pfleck]

After deserializing a VariableCondition symbol, all variables are checked. This is caused because the storable property AllVariableNames resets the VariableNames.

Connected to #1865 in which the implementation of the Variable has been corrected, but the VariableCondition was overlooked.

private List<string> variableNames;
[Storable]
public IEnumerable<string> VariableNames {
  get { return variableNames; }
  set {
    if (value == null) throw new ArgumentNullException();
    variableNames.Clear();
    variableNames.AddRange(value);
    OnChanged(EventArgs.Empty);
  }
}

private List<string> allVariableNames;
[Storable]
public IEnumerable<string> AllVariableNames {
  get { return allVariableNames; }
  set {
    if (value == null) throw new ArgumentNullException();
    allVariableNames.Clear();
    allVariableNames.AddRange(value);
    VariableNames = value;
  }
}

[mkommend]

r13616: Quickfix for deserializing the VariableCondition symbol correctly.

TODO: fire changed events and handle cases if all variables and variables are out of sync.

[gkronber]

Tested and reviewed r13616. Fine by me.

[ascheibe]

r13913 merged r13616 into stable