Added persistant storage of usernames and manga mappings

Stores MangaWatcher mhash -> MyAnimeList id maps so that subsequest syncs are faster and you do not
have to select from search results more than once.
Also stores usernames so that subsequent logins are more convenient
Now removes the synopsis before parsing MAL XML

MAL doesn't give nice XML responses, and the synopsis tags often had unescaped
HTML entities that broke the XML parser. My previous solution was to try to parse it once, then
escape each HTML entities if it failed (Since it is a lot of search and replace calls).
Now I remove the synopsis in a since replaceAll call.