Code review comment for lp:~vr123456/leo-editor/detect_urls

I have made one more improvement, that I think is important.

I have introduced an explicit 'init' function, so that info
about the plugin is published, when the cmd 'print-plugins-info'
is executed.

I have used the style found in plugin 'maximizeNewWindows.py'.

Please check especially the section << version history >>
and my 'version' choice. - I do not know if there is any
established convention, that I should follow ...