Prepare v1.12.3

CHANGELOG

+v1.12.3 2020-02-17
+------------------
+Correct the path to the user home directory on Mac OS X in the readme file
+Make sure that .gitconfig and composer's auth.json exist even before l3drun gets started, not before l3d project container starts as that's too late
+
 v1.12.2 2020-02-12
 ------------------
 Better define the destination for composer create project which is required on some Macs