Add support for "delimiters" and "useDefaultDelimiters" like the maven-resources-plugin 2.4 has

The maven-resources-plugin 2.4 added "delimiters" and "useDefaultDelimiters" which allows the default delimiter strings to be disabled and allows custom delimiters to be used.
In a project which is packaging ant files or other files which use a lot of ${*} type variables specifying a custom delimiter and disabling the defaults would be more more usefull than the other option at present "escapeString"