Re-organize and improve help command and help info for each command

libexec/tmuxifier-new-session

@@ -2,6 +2,16 @@
 set -e
 [ -n "$TMUXIFIER_DEBUG" ] && set -x
 
+# Provide tmuxifier help
+if [ "$1" == "--help" ]; then
+  echo "usage: tmuxifier new-session <layout_name>
+
+Aliases: new-ses, ns
+
+Create a new session layout and open it for editing in \$EDITOR."
+  exit
+fi
+
 # Provide tmuxifier completions
 if [ "$1" == "--complete" ]; then
   for item in $(tmuxifier-list-sessions); do