Updates to the External Authentication guide

- Added instruction on enabling/disable via appliance UI and Console.
- Extend manual configuration page to reflect changes needed
to support REST API/SOAP.
- Added instruction on how to optionally configure external
authentication using the Appliance Console CLI.
PR Review Changes to the External Authentication Guide.

- Mentioning that users must belong to groups already
created in the Appliance.
- Mentioning that enabling and disabling the feature
must be done in both the Appliance UI and the Appliance
Console.
Modified current sprint to better reflect reality.
Merge pull request #37 from chessbyte/current_sprint

Modified current sprint 12 to better reflect reality.
Remove ca from source code layout
Remove the number of directories so we don't have to maintain it.
Move Roadmap and Sprints to GitHub milestones

Also, organize the README a little better.
Merge pull request #38 from Fryguy/move_sprints_to_milestones

Move Roadmap and Sprints to GitHub milestones
Merge pull request #33 from abellotti/external_auth_guide

Updates to the External Authentication guide
Add Developer Setup guide
Alphabetize links
Merge pull request #20 from brandondunne/add_developer_guid

Add developer Getting Started guide