Change backend objects

[FCoenen22]

Change backend objects to be less complex

• ProjectReportTemplate
• ProjectReport

[FCoenen22]

The backend objects got changed but there are still open ToDos:

• Define a new data transfer object that can we used for the REST-Calls
• frontend needs to also use the same object
• DefaultProjectReportTemplate.class should get it`s values from a external file(json, xml or csv)