Impl. IntentFactory
Refactored createRandomMatrix to MatrixUtil.
Wrote function for solving linear equations.
Now LinearEquationProblem can generate non-boring system of linear
equations(it doesn't render them yet, though.)
Now the linear equations are also rendered. Also, fixed some bugs in
the random generation of linear equations.
Improved the rendering output of LinearEquationProblem.
Made the generation of equation systems faster.
Cleaned up some.
Added comment.
Localized the description of the linear equation challenge.
Improved the design of linear equation problem.
Removed debug code.
Merge branch 'linear_equation_challenge' into development

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Fixed the font of the variable in linear equation challenge.
Removed debug code.
Simple math division fix
Javadoc updates in challenge interface
Moved audio and challenge factory to subpackage (STAN issue)
ChallengeConfig params through constructor fix
Improved the javadoc in MathProblem.