Add test for :time command

notebooks/tests/time.ipynb

+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       ":time COMMAND [ARGS ...]\n",
+       "\n",
+       "Execute the given command and measure how long it takes to execute."
+      ]
+     },
+     "execution_count": 1,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    ":help :time"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`:time` works for commands."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Execution time: 1.029668114 seconds\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "null"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    ":time :groovy Thread.sleep(1000)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`:time` works for expressions."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Execution time: 1.079495268 seconds\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "{12345,24690,37035,49380,61725,74070,86415,98760}"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    ":time {x | x : 1..100000 & x mod 12345 = 0}"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "ProB 2",
+   "language": "prob",
+   "name": "prob2"
+  },
+  "language_info": {
+   "file_extension": ".prob",
+   "mimetype": "text/x-prob",
+   "name": "prob"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}