Add option to WriterHandler to collapse repeated messages

The WriterHandler could have a time interval configured wherein a repeated message would be collapsed.

The last message would be stored in a field for comparison along with a nanoTime tag (the timestamp on the message is not adequate because the clock can have skew or be reset completely at any time). If the current message string equals the last message string, and collapsing is enabled, then instead of logging the message, a count is incremented. If the current message is not equal, then the stored message is logged with a tag indicating the number of repeats (i18n?) and then the next submitted message is logged.