various fixes for developer/www.rst

* one sentence per line
* excessive indenting for lists
* missing indenting for complex list items
* use of `example.org` instead of not-really-recommended domains
* extra empty lines
make example URLs to use example.{com,org,net}

* in some cases URLs pointed to some real URL (e.g. in case of
  SourceForge)
* in some cases URLs pointed to potentially used domains
Merge pull request #1304 from sa2ajj/more-minor-docs-fixes

More minor fixes for docs