Issue #3511972 by phenaproxima, azizos, quietone, rkoller, pameeela, catch,...

Issue #3511972 by phenaproxima, azizos, quietone, rkoller, pameeela, catch, poker10, tedbow, alexpott, larowlan, gábor hojtsy, mcdruid, xjm, benjifisher, yesct: Allow Composer and rsync location to be configured via the UI

(cherry picked from commit 780342ad)