Nemseer

- Where they exist, drop intervention periods when converting to xarray and provide user with warning

- Links to examples in all functions in Core Functionality of documentation
- Detailed example of P5MIN demand forecast errors for 2021

- Various bug fixes from beta testing
- Selective conversion of CSV to parquet
- Correctly implement intervening date generation for filename generation
- Example tidied up
- Seconds can now be supplied in datetime inputs (as long as they are `00`)

- Implement `processed_cache
- Update documentation

Major features

- Compile data to xarray Dataset
- Smarter `download_raw_data` function

Minor additions

- Additional downcasting in conversion to parquet to reduce memory/file size
- Update glossary with PD/STPASA run types
- Additional info in quick start

Fixes

- Fix bug where data was mapped to enumerated table name
- Remove duplicate rows when compiling

- Implement data compilation to pandas DataFrame
- Add forecast-specific datetime validation to DataCompiler
- Handle invalid/corrupted files during compilation
- Add runtime generators
- Expand testing for new functionality
- Move constants to data module
- Expand glossary and update README, API and quick start pages in docs