New Zephyr API

[Rpan4853]

• Combined Zephyr functionality into one class. New Zephyr class acts as a state manager and is meant to provide an easier user experience when solving predictive engineering problems.
• Using a class instance for an entire machine learning problem flow can be problematic when users re-iterate on the same class
• To prevent this, implement GuideHandler with guiding messages that warn users when they will make data stale and help them get back on track
• Updated & added tests

More motivation and proposed API can be found in this thesis proposal

TO-DO:

• rem old zephyr files