openScale 2.0 release

• replaced HelloCharts library with the MPAndroidChart library
• added option to enable/disable graph legend
• replaced statistic last week/month table view with radar graph
• added rolling chart option
• added graph marker and marker menu for line graphs
• added option to enable/disable Y-axis
• change indicator color depending on if you are going towards or away from your weight goal
• fixed notification bug for Android O
• simplified Bluetooth machine state for improved Bluetooth communication