Ring ideals

[dan323]

I am adding some results on rings:

• Ring ideal definition
• Product and sum of ideals
• Prime ideal definition
• Maximal ideal definition
• Spectrum and Zariski topology
• Ring homomorphism
• Quotient of ring by ideal
• Integral domain definition
• PID definition
• Euclidean ring definition
• Ideal maximal in commutative ring iff quotient field
• Ideal prime in commutative ring iff quotient integral domain
• Ring of polynomials
• Ring modules

[dan323]

First part on MR #23