code: function(onProgress) {
          onProgress = onProgress || function() {};
          let projects = library.public_getters.getProjects();
          library.autosave(false);
          return promiseUtils.chain(downloadChunks, function(err, data) {
              if(err instanceof Error) return Promise.reject(err);
              console.log(err);
              return false;
          }, {compact: true, onProgress: onProgress.bind(null, 'chunks')})(projects)
              .then(function() {
                  library.commit();
                  library.autosave(true);
                  return Promise.resolve();
              })
              .catch(function(err) {
                  library.autosave(true);
                  return Promise.reject(err);
              });
      }
docs: Downloads the chunks for all projects
  @param onProgress
  @returns {Promise.<>}