Add CWExpenseEntry Class

[BrianBtheITguy]

Create function to add expense entries.

Create Add-CWExpenseEntry Advanced Function
Create Get-CWExpenseEntry Advanced Function
Create Remove-CWExpenseEntry Advanced Function
Created Pester Tests for the Above

(copy/pasted from your CWTimeEntry issue - this would be a sweet addition and likely when I get some time I'll look through your code and see if I can build it out myself - if so i'll post the scripts up here)