Docker improvements and enabling auto testing

[igorpecovnik]

Description

Rework Docker install and enable automated testing routine.

Implementation Details

Rework Docker install to use wget only. We don't need to use Curl and wget. When using BASH 4+ (which we do), we can use internal function to conduct lowercasing. Also improve purging by deleting the key and sources.

Testing Procedure

• Auto testing enabled and successful

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have ensured that my changes do not introduce new warnings or errors
• No new external dependencies are included
• Changes have been tested and verified
• I have included necessary metadata in the code, including associative arrays