Releasing as Quick DER 1.0

The code has been tested in various applications and appears to do its work well, though we had to remove a few oversights. Since the code now feels as "sufficiently tested", we hereby release a first 1.0 series release.

We follow https://github.com/arpa2/howto/blob/master/release.md so we will not release a 1.0 proper; we leave it to distributors of packages to name a package 1.0.n where n can be their own series that increases with the RC-number, in any way they like.

Upcoming versions may include additional utility routines for processing INTEGER values, and possibly more. In our early development we already found these to be useful in several situations. Until then, you may want to search src/starttls.c in the TLS Pool for the qder2b_ functions.