Class IntegerDimEnc shuould give more exception information when the length is exceed the max or less than the min

the message IllegalArgumentException in Class IntegerDimEnc is empty currently, it may cause confusion when using Kylin or troubleshooting a problem. 

// code placeholder

public IntDimEnc(int len) {
if (len <= 0 || len >= CAP.length)
throw new IllegalArgumentException();
this.fixedLen = len;
}