Add Version bump script

[kskarthik]

This script will automate the chore of changing of versions across multiple files when there is a release.

It expects to be run from the project's root:

Example: GlobaLeaks/scripts/bump_version.sh 4.30.3

The CHANGELOG file only must be manually edited.

This saves the valuable developer's time.

• The pull request should include a description of the problem you're trying to solve
• The pull request should include overview of the suggested solution
• If the pull requests changes current behavior, reasons why your solution is better.
• The proposed code should be fully functional
• The proposed code should contain tests relevant to prove is functionality
• The proposed tests should ensure significative code coverage
• All new and existing tests should pass