Interface representing a list of all installed extensions
Determines if an extension exists with the given id.
| aId | The id of an extension |
| true if an extension exists with the given id, false otherwise. |
Gets a extIExtension object for an extension.
| aId | The id of an extension |
| An extension object or null if no extension exists with the given id. |
Array of extIExtension listing all extensions in the application.