The documentation states that the debugging jar is called
smackx-debug.jar. However, according to maven central, that name was
only used until 3.2.1, newer releases (including 4.4.0-alpha1) only
distribute smack-debug.jar, which contains the debugger as advertised.
and rename documentation links from .html to .md, since
markdown-gradle-plugin will now automatically transfer the links .md to
.html.
Now users can broswe the documentation in their markdown form (e.g. via
github) and via html.
Also add a symlink from README.md to index.md in documentation/.
