Cbi settings

[seamustuohy]

This commit will restructure the way that nodogsplash is handled in the luci menu's.

SEE: opentechinstitute/luci-commotion#195
SEE: opentechinstitute/commotion-feed#50

To Test:

1. Build and image from the following commotion-feed branch: "commotion-splash-cbi"
2. Add the following branches for makefiles to pull from:
   luci-commotion-splash: cbi_settings
   luci-commotion: commotion-splash-settings
3. Complete the setup wizard.
4. Enable the welcome page in "Basic --> Client Controls"
5. Confirm that the welcome page was added.
6. Go to "Advanced --> Services --> Captive Portal"
7. Perform a variety of nodogsplash configurations on this page.
8. Confirm that the nodogsplash config file is correct
9. When nodogsplash is supposed to be on confirm that ndsctl status affirms the correct setttings
10. when off, ndsctl status should show it as off.
11. All settings should be reflected in the splash page options