LINEAR: Compute the implication graph for linear magmas (Part 1)

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As a first step for #364, I have created some scripts and data files.

linear_magmas/list_restrictions.py reads all equations, inserts x ◇ y = a*x + b*y as the operation, expands the equation assuming that a and b don't commute, and computes the coefficient of each variable in the equation. The result is written to data/linear_magma_restrictions.txt.

Example:

Equation101 x = x ◇ ((x ◇ y) ◇ x) 
-> (a*x + b*(a*(a*x + b*y) + b*x)) -(x)
-> a*x + b*a*b*y + b*a**2*x + b**2*x - x
-> [b*a*b, -1 + a + b*a**2 + b**2]

linear_magmas/reduce.py then uses this list and calls Singular to compute a Gröbner basis for each set of restrictions. This is done once assuming commutativity and once without.

The restrictions for Equation101 then become: [ab+b**2+a-1, a**2-b**2-2a+1, b**3-b**2-a-b+1] and [ab+b**2+a-1, a**2-b**2-2a+1, b**3+ab-b]