Load a new context
@param {Object} state Current state.
@param {Object} action Action to handle.

@returns {Object} The new state.
function setContext(state, action) {
  let metadata = incrementVersion(state.metadata, SOURCE_VERSION_KEY);
  metadata = incrementVersion(metadata.metadata, LAYER_VERSION_KEY);
  return Object.assign({}, action.context, {
    metadata: Object.assign({}, metadata.metadata, action.context.metadata)
  });
}