Add version information to *-config.cmake files

[jamiesnape]

The presence of *-config-version.cmake files not withstanding, it is common to include version information in *-config.cmake files for ease of use by downstream projects.

[jslee02]

This change would be essential when an octomap dependent package wants to support for multiple version of octomap. FCL is doing in this way for instance. However, we couldn't use octomap-config.cmake file for this purpose (currently using pkg-config) since it doesn't convey the version information.

[ahornung]

I'd rather have this separately tracked from this PR in #138 (same for the other ones)

[jamiesnape]

Removed.

[ahornung]

@jslee02 I see, thanks for the quick explanation. I haven't seen providing this information in two places at the same time for CMake before (also not mentioned by the CMake docs), so I'm really wondering if that can't be done with the regular version info.

[jamiesnape]

I haven't seen providing this information in two places at the same time for CMake before

Pretty common, for example, these Kitware projects:

• https://github.com/Kitware/ITK/blob/master/CMake/ITKConfig.cmake.in#L15-L17
• https://github.com/Kitware/ParaView/blob/master/ParaViewConfig.cmake.in#L22-L25
• https://github.com/Kitware/VTK/blob/master/CMake/VTKConfig.cmake.in#L26-L28