Implementatie Chart: met bug (wordt niet weergegeven in listheader)
Update Chart-Library v1.7.1
Merge branch 'master' into ChartLibrary

Conflicts:
	NotificationAnalyser/app/src/main/java/com/tierep/notificationanalyser/HistoryFragment.java
Refactor: verwijderen oude BarChart code
HistoryFragment: bugfixes
MPChartLibrary : snelle bug fixes, a more permanent fix has to be developed.