urdfdom should find_package(TinyXML) in urdfdom-config.cmake about urdfdom

[traversaro]

If the final goal is a relocatable package that does not hardcode the location of TinyXML nor the install location of urdfdom, during the build, it probably make sense to make sure that the FindTinyXML.cmake installed by urdfdom creates an imported target, and urdfdom creates an imported target as well.

One tricky aspect is that the urdfdom-installed FindTinyXML.cmake may risk to shadow an existing FindTinyXML.cmake already used by the user, so perhaps it could make sense to use urdfdom prefixes and just add FindTinyXML.cmake to the CMAKE_MODULE_PATH only as long as strictly necessary.