Escape sequences gets stuck with "Illegal group reference" error if replacements have '$' chars.

When shipping data to hbase sink, we use regex matcher to handle escaping. Apparently there are some problems in the code due to particular strings that replace the escape sequences.

When doing regexes $ needs to be escaped to be \$, and \ needs to be escaped to be
in the replacement strings.

This seems like a relevant example:
http://cephas.net/blog/2006/02/09/javalangillegalargumentexception-illegal-group-reference-replaceall-and-dollar-signs/

This may explain some mysterious errors.