Make graphs in section page collapsible.

Also collapsible for graphs in section.

Fold (and expand) graphs on service by clicking `+` beside graph name.
Folding / expanding all graphs at the same time is also available.

http://gyazo.com/a27241893a2db1ffd2a1208f73ce02ef
![preview](http://gyazo.com/a27241893a2db1ffd2a1208f73ce02ef.png)