Added RFC 4180 functionality to DelimitedLineAggregator.

Using the DelimitedLineAggregator in combination with arbitrary objects is problematic as their string representations may contain the delimiter, quotes or newlines. This breaks most readers. 

I've added RFC 4180 functionality. The implementation is such that records are not quoted when not needed. The quote, newline and delimiter can be changed.

A possible improvement could be moving the code into StringUtils.