Release 3.1.0

• implement templates support (#71)
• implement special functions (#71)
• special directory for configs (#72)
• custom bar images (#80)
• custom bar values (#80)
• show changelog after updates
• add Polish translation (thanks to Mariusz Kocoń)
• use Qt-5.6 features
• fix invalid tooltip resize in desktop panel (#74)
• fix graphical items blinking (#81)
• drop tasks and move to native QProcess to avoid crash (#83)
• the newest Qt (5.6) fixes
• the newest Plasma fixes
• move from OWM to Yahoo! Weather (#73)
• improve performance by using optimized subscriptions (#75)
• improve performance by storing QVariant instead of frequent casting (#75)
• change bar names semantic to the simplest one (#80, breaking changes)
• high memory usage notifications have been changed from 90 to 80 perc
• a large part of refactoring