Add Numerically Equal and Relatively Equal comparisons in math helper class

[osrf-migration]

Original report (archived issue) by John Hsu (Bitbucket: hsu, GitHub: hsu).

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Current comparison strategy math::equal is using primitive absolute magnitude comparison. This may not be sufficient in some cases, for example where relative magnitudes are large, or the values being compared border numerical precision boundaries.

Per @sherm1 recommendation in pull request #82, we should add math::numericallyEqual and math::relativelyEqual.

Also, see issue #42 for extension to Vector3 class.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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• Edited issue description