Add BUILD_RELEASE to main kstars version display.
Taking the recent change a step farther, this adds the BUILD_RELEASE string to the main version display in the 'About KStars' window and the splash screen.
See https://photos.app.goo.gl/DDYJwx4EjCwcSbML7
Testing
Start KStars, Click Help --> About KStars Should show the above link, particularly "KStars Version 3.5.0 Beta"