[scripts] add Python calculator

scripts/pycalc3

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+for python in bpython python3; do
+  if python="$(command -v "$python")"; then
+    break
+  fi
+done
+echo "using Python '$python'"
+PYTHONSTARTUP="$(dirname "$0")/pycalc_startup.py" "$python" "$@"

scripts/pycalc_startup.py

@@ -0,0 +1,3 @@
+from math import *
+
+print("loaded Python calculator")