Fix missing services in demo, fix README files, add missing CSS for fediverse and remote flattr

[richard67]

This pull request (PR) fixes several issues mainly caused by recently merged PRs.

1. Add missing less file for the recently added "fediverse" (Mastodon) service so that buttom becomes visible (without that the button is white on white and so invisible). The colour has been taken from their site https://joinmastodon.org/ .
2. Change icon of that service from "lock" to the Mastodon brand icon.
3. Fix duplicate "data-services" row in parameter documentation which is caused by a merge conflict, see also 7c1f0f6#r127809094 .
4. Fix wrong service name "tencent-weibo" instead of correct "tencent" in README files and demo/index.html - this seems to be an older issue.
5. Add missing services to README files and list them in alphabetical order.
6. Add missing services to first 3 examples in demo/index.html and use them in alphabetical order, except that the "internal" links for services "clipboard", "mail", "print" and "info" come as last.
7. Synch the German README file with recent changes in the English one (https and example code).
8. Remove "flattr" service as it has been discontinued, see PR Remove Flattr service shariff-backend-php#190 and the referred issue in the shariff-backend-php repository.