add in altitude support and simplify adding detector function

[ahnitz]

• Adds in the ability to set the altitude angles for custom detectors
• Simplify detector class, use lal only for its detector location information rather than the response value itself. This makes it easier to provide consistent metadata between custom and lal-builtin detectors
• Simplify the add detector on the earth function (use matrix multiplication operator, make the rotations clearer / more obvious / start rotations from simpler form of the basic arm response)

Todo

• update unittest to include both use of custom detector and crosscheck response matrix calculation against builtin lal value