client/container: implement debug log-levels

DOCKER_FINANCE_DEBUG will now support the following:

0 = no debug output
1 = `print_debug` (bash/PHP)
2 = level 1 + `set -xv` (bash)

client/src/docker/docker.bash

@@ -161,7 +161,7 @@ function main()
   lib_docker::docker "$@" || lib_utils::die_usage "$_usage"
 
   # shellcheck disable=SC2154
-  [ "$DOCKER_FINANCE_DEBUG" == true ] && set -xv
+  [ "$DOCKER_FINANCE_DEBUG" == 2 ] && set -xv
 
   #
   # Command facade