Sort narrower concepts by notation on concept page

[osma]

At which URL did you encounter the problem?

http://dev.finto.fi/gfdc/fi/page/C4

What steps will reproduce the problem?

1. Use a classification which has notation codes, e.g. GFDC (above URI)
2. Look at a concept with narrower concepts

What is the expected output? What do you see instead?

Expected to see the narrower concepts on the concept page sorted by notation. Instead they are sorted alphabetically.
The narrower concepts (and related etc.) should be sorted by notation, just like in the hierarchy view.