Add an inital label value when editing tree items label

[mcharfadi]

• EditingContextRepresentationDataFetcher will filter on IRepresentation unstead of ISemanticRepresentation to be able to support TreeDescription. As such targetObjectId is removed from RepresentationMetadata.

• The GraphQl input TreeEventInput now have an attribute treeId that start with "explorer://" when it's the explorer.

• A React component TreeItemDirectEditInput and the interface IInitialDirectEditTreeItemLabelProvider on the back-end are created.