This PR includes two tweaks:
* it helps avoiding the bug querying OCSP responder #2329 by adding
openssl. The openssl supplied has a mimor DNS lookup problem due
to glibc / musl libc compatibilty issues
* by adding openssl also it helps a bit for some performance problems
related to other projects, see #2314
Also the git binary is removed (#2315).
Thanks to @polarathene for the discussions
.. see also #1559.
It "mkdirs" the needed etc and bin directories first, then copies
stuff over. It also reduces a few layers.
Also it corrects a mistake in the Readme.md (docker exec --> run)
... and at the same time allow correct local builds --
the default branch is 3.1dev at the moment.
It still clones the repo from github which isn't
needed. A pure copy command would be the best. However
it might cause other problems.
See also #1559
