Change name of physics package 'cam_dev' to 'cam7'

[brian-eaton]

#813 - Introduce "-phys cam7" and remove "-phys cam_dev".
Related changes:

• The compset tokens CAM%DEV are replaced by CAM70
• The src/physics/cam_dev/ directory is renamed src/physics/cam7
• No compset names were changed.

N.B.: This PR depends on a CMEPS tag to make the corresponding change of CAM%DEV to CAM70 in buildnml

. resolves #813