Improve usability for --physics option

[osrf-migration]

Original report (archived issue) by Jose Luis Rivero (Bitbucket: Jose Luis Rivero, GitHub: j-rivero).

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We could improve the way of handling the -e or --physics option in the gzserver.

When passed an invalid value gazebo is starting with given any hint to the user about the fallback option taken or the error.

gazebo -e non_valid

For extra points, try to detect if the support for one of the physics engines is not implemented and don't allow the user to run the -e option with the unsupported physics engine.

[osrf-migration]

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

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If you do --verbose there will be an error message.

[osrf-migration]

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

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It could be improved though, currently we list all 4 physics engines as options in the --help message even if the other engines aren't installed.

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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• set version to "all"