ArrayProxyList.indexOf doesn't work correctly with 'sliced' proxies

[jenetics]

When searching for the index and an element is found, the start index of the used ArrayProxy must be subtracted:

// In org.jenetics.internal.collection.ArrayProxyList class.
for (int i = proxy.start; i < proxy.end && index == -1; ++i) {
    if (element.equals(proxy.__get__(i))) {
        // Subtract the start index of the used proxy: 
        // index = i - proxy.start;
        index = i;
    }
}

[jenetics]

Fixed: #3