Organize nodes by area/level of math

[kevinbarabash]

Examples:

• basic (operations, variables, relations)
• algebra (system of equations, functions, trig, sequences and series)
• linear algebra (vectors, matrices)
• calculus (limits, derivatives, integrals)
• geometry (points, lines, shapes, angles, etc.)
• units/measurement
• logic

A potential issue with approach is that some node types might be use in multiple areas but with different constants, e.g. Operation uses dot and cross product for linear algebra.