Implementing Menu based builder, Package Caching, Multi Variant builds, Automated builds for CI and minor improvements.

Script Overhauling

• There are significant changes to the script, a lot of overhauling
• Division of parts of the script into different functions
• Adding a check to make sure that the script is being run with administrative privileges

New Features implemented

• Adding an option for cleaning the build environment before starting new builds
• Implementing package caching for local builds. While doing the development, a lot of time is wasted for downloading the packages again and again during the build. This time could be saved by caching the downloaded packages using apt-cacher-ng
• Added some more packages to the initial setup apt-cacher-ng figlet
• Using figlet to showcase significant parts in the script.

Closes #17 and #18