Migrate most origin-server documentation

* I've taken all of the individual documentation of built-in cartridges and made on Cartridge Guide
* I've taken Jhon Honce's work to create a Cartridge Developer's Guide and added to the User Guide
* In general, I've taken all of the documentation that was scattered throughout the system and consolidated it under the [origin-server]/documentation area.

The net result is that almost all of the documentation created by various developers over the past few years is now centralized and a lot easier for people who are not looking at the origin-server repo to find.

I think that this change brings us a long way towards having the kind of comprehensive, accessible documentation that people in the Origin community are looking for. I also think that this is a big change, and so I am looking for buy-in from the folks who will actually benefit from this re-organization.