template: update test

- rely on the VleBuildAllTest cmake command
- rename test.cpp to test_packages.cpp, test is a common target for make which
 causes a confusion between the standard test target and the compile unit.
CMake: improve debug for VleUtilsConfig.cmake

Some messages have been added in the Debug mode.
app/vle: add a '\n' at the end of error message

A missing '\n' is added for message to the standard error stream when an
exception is caught.