public Object dropLowest() {
            final int lpOld = lp;
            if (++lp == binsize) {
                unlink();
            } else {
                lv = al[lp];
            }
            final Object res = vla[lpOld];
            vla[lpOld] = null;
            return res;
        }
add a key value pair to the heap

@param key   the key to insert
@param value the value to insert object
main/src/main/java/cgeo/geocaching/brouter/util/SortedHeap.java