Update documentation with switch site and Django style filters

[jorwoods]

Updates documentation to have details for site switching and the django style filtering

[bcantoni]

@jorwoods thanks for adding all this. I actually already added docs for switch site in #701, so I'm not sure why they aren't in your branch. You might need another merge from (or rebase on top of) gh-pages.

[jorwoods]

@bcantoni It was indeed out of date. I did another merge and removed my duplicate entries for the switch site documentation

[bcantoni]

@jorwoods thanks for this contribution!