Load big groups

My intension:
I wanted to make the big groups loadable.
The groups "Jeder", "Korporationen" failed to load. 

My changes:
1. For groups with more than 260 descendant users, the google map is not filled.
2. for each displayed member in the member list, 1 SQL statement less is executed

The effect:
After rails server restart the loading times are slightly higher than the second time. 
"Jeder" can be loaded in 18 respective 4 seconds.
"Korporationen" can be loaded in 7 respective 5 seconds.