UC14

This PR implements the third subflow of UC14, which allows a registered HCP to view diagnosis trends for 8 weeks up to a provided date.

To do this, additional functionality was added to the DiagnosesDAO and to the GetDiagnosisStatisticsAction to pull the required data from the database. In addition, the frontend was modified to display the chart.

To run the tests, enter the following commands:

• mvn install -DskipTests
• mvn test -Dtest=ViewDiagnosisStatisticsActionTest
• mvn test -Dtest=DiagnosisTrendDataTest
• mvn test -Dtest=ViewDiagnosisStatisticsTest