v3.24: 4 Nov 2020 - Minor updates

A small update with a few minor improvements.

• New column "Billable Expense Burn" available on the project directory
• New column and grouping for default billing method (T&M or Fixed) added to the projects and invoices directory screens
  • The billing method is set on the setting screen for a project
• Add expense button added to the expense screen within the project workbench
• There have been no changes to the SQL views