parentheses in performTermOperationOnExpression

[rshconn]

Modified performTermOperationOnExpression to add parentheses only for /, *, and ^ operations per #115. Created new test function testPerformTermOperationExpressionStep to test the equation at a given step.

Tests cover +, -, /, and * cases:

• (From #115) x + 1 = 2 -> x + 1 - 1 = 2 - 1
• (From #115) 2y = 2x + 2 -> y = (2x + 2) / 2
• x - 1 = 2 -> x - 1 + 1 = 2 + 1
• y/2 = 2x + 2 -> y = (2x + 2) * 2