Improve *.tar.gz detection mechanism during image build

[jshaptala]

Right now, the mechanism of *.tar.gz file detection has flaws when it comes to more than one software package placed in the /files directory.

We need to make sure we select the proper file with the right extension *.tar.gz. And if the incorrect package is selected, the image is not built and the error is shown. In case of multiple files in the directory that are matching a pattern, let's use the package with the newer version. Otherwise, we can start with the first file in the list.

Suggested error message: Error. Docker image build failed: Invalid application package detected.