Update dataset_processor function parameter documentation

- Update the dataset_processor function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update data_source.local function parameter documentation

- Update the data_source.local function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update data_source.rcmed function parameter documentation

- Update the data_source.rcmed function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update metrics function parameter documentation

- Update the metrics function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
- Minor documentation changes for clarity.
Update utils function parameter documentation

- Update the utils function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
- Minor documentation changes and rewordings for clarity.
Resolve CLIMATE-479. Merge PR #81.