Expense edit has to be enabled

The expense viewer by default has the controls disabled until the Edit
button is pressed
Entity class for income added

Any dependencies had entity classes added also
Added IncomeViewer form

The form next needs to be connected to the data viewer
Connected the Income Viewer to the Data Viewer, closes #21

The Incomes can now be edited from the program
Merge pull request #27 from M-Zuber/Development

Added feature for updating income