be8ae96098
When a project is packaged for redistribution the local package registries should not be updated or consulted. They are for developers. Add variables to disable use of package registries globally: * CMAKE_EXPORT_NO_PACKAGE_REGISTRY that disables the export(PACKAGE) command * CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY that disables the User Package Registry in all the find_package calls. * CMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY that disables the System Package Registry in all the find_package calls. Update documentation and unit tests.