Docs: update some index references

As I was updating some stuff for the clustered service, I saw some weirdness in the 'index' page.

Fixes:
 * change a semi-colon to colon for the "single" index
 * 'gerrit integration' shows up under Properties, and that doesnt seem like the right place. Although I'm not sure if the place I did put them is right either... up for comment :)