function initVersioning() {
		return VersionsAPI.initialize({
			control: this.getRootControlInstance(),
			layer: this.getLayer()
		}).then(function(oModel) {
			this._oVersionsModel = oModel;
		}.bind(this));
	}
Inits version models. Clears old state if RTA is starting from end user mode (no switch)
@returns {Promise<void>} - Promise