The order of property set rows should be kept

When playing with property sets, the order of rows is slightly different each time.

To reproduce:

• create test1-12 all at the same time
• after saving, they're ordered alphabetically: test1, test10, test11, test12, test2.
• edit test2 & save. The order is: test1, test7, test8, test9, test10, test11, test12, test2
• edit test8 & save: test1, test4, test5, test6, test7...
• edit test1 & save: test1, test12, test2, ...
• edit test11 & save: test1, test9, test10, ...