Masking support for 8-digit BINs

[ISOUtil#protect()](https://github.com/jpos/jPOS/blob/c5735364e910e8b552924038660bc2c11f2ec2b6/jpos/src/main/java/org/jpos/iso/ISOUtil.java#L903) should have configurable/dynamic masking of PANs to support 8-digit BINs

Come up with a flexible and backward-compatible (default) solution.
