OrderedDictionary instances not correctly stringified to json or javascript

[jbrichau]

In Pharo7, it seems the use of PluggableDictionary has been replaced by OrderedDictionary in some places (e.g. Collection>>#groupedBy). However, Seaside does not define correct json conversion for instances of OrderedDictionary. For example, the following code snippet:

|dict|
dict := OrderedDictionary new add:(#foo -> 'test1');add:(#bar -> 'test2');yourself.
dict asJson

Will produce:
["test1", "test2"]

This should be:

{"foo"->"test1", "bar" ->"test2"}

OrderedDictionary existed before but since it's now used in key methods of the image to construct dictionaries (like #groupedBy), we should implement the necessary json and javascript conversion methods on it.