Fixing documentation issues

[dcoeurjo]

PR Description

This PR contains documentation fixes (starting with some geometry module pages). I'll update this PR, I'm just creating it to keep you in touch.

Checklist

• Unit-test of your feature with Catch.
• Doxygen documentation of the code completed (classes, methods, types, members...)
• Documentation module page added or updated.
• New entry in the ChangeLog.md added.
• No warning raised in Debug cmake mode (otherwise, Travis C.I. will fail).
• All continuous integration tests pass (Travis & appveyor)

[dcoeurjo]

can someone check this one?

[jlevallois]

Seems good for me (except for the #pragma GCC diagnostic ignored "-Wdeprecated-declarations" part because I don't know why you need this).

[dcoeurjo]

some GCC/CLANG compiler complain due to warnings in ITK/Eigen which are not related to DGtal.

Thanks, merging,