We noticed the possibilities of invariants inside the bip32
module. This commit Wants to cover all possible invariants of the bip32
indexes changing the enums with value to newtypes that only could be
instantiated from its functionalities and constructors, especially while
dealing with hardened indexes. Hardened indexes automatically defines
its index while being casted, becoming infalibble to cast a Hardened
index from a u32 value and the inner value is arbitrarily exposed with
the accordingly value conversion, sucessfully covering cases with and
without hardening notation.

	Naming changed, while dealing with key indexes we replaced the
keyword and concept to "index" instead of number to better represent
its unique function.