Revert 170d204..96fe2ab

This rolls back to commit 170d204959f3de4d51ad2d052f2ec3605b95da2b.
Revert "finish navigation"

This reverts commit 3f9ca69848409599c5849d333931c214cef13850.

Conflicts:
	Base.lproj/Main.storyboard
	MultiplicationChooseViewController.swift
	StudyTypeViewController.swift