HPCC-10028 removeEntry() should pass the error message to the caller

Add new removeEntry() method with suggested StringBuffer parameter.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
HPCC-10028 removeEntry() should pass the error message to the caller

Rework after first review.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>