Feature: Show application statistics

[Mtze]

It would be great to have some statistic for the current selection (filters) of applications.

Basic Statistics:

• Gender (Bar chart / Pie chart)
• Nationality (Bar chart / Pie chart)
• Devices (Bar chart - including "none")
• Scores (Bar chart)
• Study Program (Bar chart / Pie chart)

Advanced Statistics (these may replace the respective basic statistics - to be discussed):

• Score per gender (Bar for each score - multiple colors for number of applications with gender x)
• Score per nationality (Same as above)
• Score per study program (Same as above)

The statistic may be expanded in the future