Add plugin.info.txt, remove obsolete getInfo-functions
Fix accessing possibly undefined variables
Use current Gravatar API including their monsterid fallback + ssl support
Plugin adopted and new version released

Changes:
  * Use current Gravatar API
  * Use local monsterid or fallback images only if no valid mail is
    available, else the monsterid fallback from Gravatar is used
  * Request the Gravatar image over SSL if DokuWiki is accessed over SSL