Move TaskThunderbirdWin to new repository

[sea5kg]

1. Please move source code from coex/sources/TaskThunderbirdWin
   to new repository like "coex-plugin-task-thunderbirdwin"
2. Make lib.pro inside new project (see example: https://github.com/tusur-coex/coex-plugin-task-searchgitrepo)
3. Make app.pro inside new project (see example: like https://github.com/tusur-coex/coex-plugin-task-searchgitrepo)