Add oo-admin-geartop

oo-admin-geartop provides a `top` like summary of per gear CPU and Memory consumption with an understanding of cgroups resource limits.

Example output :
```
            GEARTOP -- Update: 3s  Sort: cpu_pct  09/11/14 14:16:43             
                 uuid              mem_MB   swap_MB  cpu_total cpu_quota% throttled cpu%
         5411e6a83a0fb2d397000014    70.51     0.00      45.24    100.0       5.49 104.15
         540f72243a0fb2f854000001    16.04     0.00      15.39    100.0       0.05  0.00
-- displaying 2 gears. Press CTRL-c twice to quit.
```
Choose only one method to execute commands. oo_spawn() preferred. But mixing %[] and system() makes security people nuts.