Add a script to transform output into CSV format

It is useful to debug differences between implementations, e.g.:
```sh
$ while ./create_measurements.sh 1000 && diff <(./calculate_average_royvanrijn.sh 2>/dev/null | ./tocsv.sh) <(./calculate_average.sh 2>/dev/null | ./tocsv.sh) ; do echo OK; done
Created file with 1,000 measurements in 50 ms
60c60
< Bucharest;-2.9;2.9;6.1
---
> Bucharest;-2.9;2.8;6.1
265c265
< Petropavlovsk-Kamchatsky;0.9;9.3;17.7
---
> Petropavlovsk-Kamchatsky;0.9;9.2;17.7
```

For #14

1 files changed, 32 insertions, 0 deletions

diff --git a/tocsv.sh b/tocsv.sh
new file mode 100755
index 0000000..7e9503a
--- /dev/null
+++ b/tocsv.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+#
+#  Copyright 2023 The original authors
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+exec sed '
+#
+# Transform calculate_average*.sh output into semicolon-separated values, one per line.
+#
+
+# 1. remove "{" and "}"
+s/[{}]//g;
+
+# 2. replace "=" and "/" with semicolon
+s/[=/]/;/g;
+
+# 3. id may contain comma, e.g. "Washington, D.C.;-15.1;14.8;44.8, Wau;-2.1;27.4;53.4"
+# so replace ", " with a newline only if it is preceded by a digit
+s/\([0-9]\), /\1\n/g
+'