Primitive roots and cyclic groups

[Bodigrim]

This branch is aimed to provide tools dealing with primitive roots as per #62. Despite the task sounds pretty humble, it required a lot of preparations such that:

• New Math.NumberTheory.Powers.Modular module, providing efficient and polymorphic modular exponentiation.
• New Math.NumberTheory.Prefactored module, featuring new numeric data type, which stores a number with its factors.

The main module Math.NumberTheory.Moduli.PrimitiveRoot introduces a data type for cyclic groups or residues and routines for search of primitive roots.

[cartazio]

This looks great. I’ll have to dig into it. Keep up the great stuff :)