Partial documentation for load balancers

I will be traveling for a few days so I won't be able to make much progress on this. So I thought I'd submit what I have in case you want to accept it for the upcoming release (1.9.2). If not, no big deal; I'll resume work on this next week and get it done for the release after next (1.9.3).

A preview of this documentation can be seen at https://github.com/ycombinator/php-opencloud/blob/working/docs/userguide/LoadBalancer/README.md and https://github.com/ycombinator/php-opencloud/blob/working/docs/userguide/LoadBalancer/USERGUIDE.md (which is linked off the README.md).