JSONCollection (gb.util.web)
This class represents a 
JSON object.
It is a collection that allows to associate a Null value with a key, which
is not possible with a standard Gambas collection.
Consequently:
  - 
To make the difference with a non-existent key, you have to use the Exist method.
- 
To remove a value, you have to use the Remove method.
It is used by the 
JSON.FromString() method when its 
UseNull argument is set.
Inherited properties
| Count | Returns the number of elements stored in the collection. | 
| Default | Return or set the collection default value that is returned when no value is associated with a key. | 
| Empty | Return if the collection is empty. | 
| First | Returns the key of the first element inserted in the collection, or NULL if the collection is void. | 
| Key | Returns the key of the last read or last enumerated element. | 
| Keys | Return a string array of all collection keys. | 
| Last | Returns the key of the last element inserted in the collection, or NULL if the collection is void. | 
| Length | Returns the number of elements stored in the collection. | 
| ReadOnly | Return or set if the collection contents is read-only. | 
Methods
| Copy | Returns a copy of the collection. | 
Inherited methods
| Add | Adds an element to the collection. | 
| Clear | Clears the collection. | 
| Equals | Returns if Collection is equals to the current collection. | 
| Exist | Returns if something is associated with this key in the collection. | 
| Insert | Insert the contents of Collection into the current collection. | 
| Remove | Removes an element from the collection. |