Fix dig SOA lookup

Handle dig failure

Test using Dynu.com as well as Duckdns.org

Issue #614: Fix delimiter issues with ${alldomains[]} in create_csr()

Wrong SANS when domain contains a minus character

A regexp to extract 'Subject Alternative Name' doesn't work when the domain use a minus character.

For grep regexp, to lose its special meaning inside brackets, the minus character must be placed in the first or last position in the list.

https://www.gnu.org/software/grep/manual/grep.html#Character-Classes-and-Bracket-Expressions

- use \n as delimiter for read to array
- use \n as delimiter for comparing SANs

mktemp not working correctly on Alpine Linux (added XXXXXX to template)

Fixes #612

Release v2.31

Fix bug with nslookup server param

Reference:
- https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#cmd

> The `CMD` instruction should be used to run the software contained in
your image, along with any arguments. `CMD` should almost always be used
in the form of `CMD ["executable", "param1", "param2"…]`

This change will drop the history of the repository when cloning, which
will save bandwidth and disk space, speed up the clone and checkout
process during the test and Docker build process.

Fix indentation to two spaces in other_scripts/cpanel_cert_upload

Follow EditorConfig, use consistent space indent in Nginx test configs

Correct Makefile indentation in .editorconfig

Add "Table of Contents" in README.md

Make markdownlint happy about README.md

```
README.md:1 MD041/first-line-heading/first-line-h1 First line in file should be a top level heading [Context: "![Run all tests](https://githu..."]
README.md:2 MD022/blanks-around-headings/blanks-around-headers Headings should be surrounded by blank lines [Expected: 1; Actual: 0; Above] [Context: "# getssl"]
```