Enforce equal field count in Writer

[osiegmar]

FastCSV allows the enforcement of equal field count in the Reader (via CsvReaderBuilder.ignoreDifferentFieldCount(boolean)). This allows for failing fast on malformed CSV files. However, the Writer lacks this feature.

The idea is to add a similar option to the Writer, which would throw an exception if the number of fields in a record does not match the expected count (either explicitly set or inferred from the first record).

Additionally, this could also prevent empty lines from being written to the CSV file (via calling CsvWriter.writeRecord(String...) without any arguments).