v0.42.0

Documentation:

• Many JavaDoc additions and extensions.
• Update documentation readme to include all project javadoc links (#1022)

Enhancements

• Wrap IOException for file reads (#1021). IOException is caught and re-thrown wrapped in a runtime exception RuntimeIOException. For interactive work, this greatly reduces the number of exceptions that need to be caught. Writes will handled in the next release.
• Cleanup on aggregate function names (#1020). Abstract AggregateFunctions were given a consistent name structures. All class names now have the form: [columnType][returnType]AggregateFunction (e.g. BooleanIntAggregateFunction). If the column and return type are the same, it is not repeated (e.g. StringAggregateFunction).
• Some aggregate function classes were made public so library users can subclass
• A few methods were added to Column subclasses. Notably, an asSet() method was added to columns where it was not already present.
• improved error message for Column append methods (#1019)