improved doc, added missing headers, file manipulation error management improved

init.sh

@@ -7,7 +7,15 @@
 # The complete license agreement can be obtained at:
 # https://opensource.org/licenses/BSD-3-Clause
 # ------------------------------------------------------------------------------
- 
+# Global variables:
+#  * INSTALL_MODE: if dev is declared here, packages will be installed one by
+#    one instead of sending the whole package list to the package manage
+#  * LOGFILE: Define manually output log file name. Can be superseeded through
+#    command line parameter. ATTENTION: That variable cannot be set in
+#    configuration file as it is treated before loading those, so it must be
+#    defined before calling that script.
+# ------------------------------------------------------------------------------
+
 # trace ERR through pipes
 set -o pipefail