Made superclass revenue, and expense and income. Scraped previous income idea

src/main/java/no/ntnu/idatt1002/demo/TotalIncomeIdea.java

src/main/java/no/ntnu/idatt1002/demo/expense.java

src/main/java/no/ntnu/idatt1002/demo/income.java

src/main/java/no/ntnu/idatt1002/demo/revenue.java