ssdd v1.5 released

Version 1.5 comes with tiny, but important changes.

• Renamed About button to Settings.
• You can now configure the command for each of the buttons.
• The About dialog is now in its own tab next to Settings.
• PREFIX in the Makefile is now configurable. README.md is updated to reflect this change.

This means that you can now configure the command used for every button and if you're using a system without SystemD, you are now free to use other commands. I'm using Mageia Linux and it uses SystemD, hence the default in the first few releases.

Enjoy!

Full Changelog: v1.4...v1.5