Setting: voucherNumber is editable (Boolean) and Add prefix to voucher number

Overview: some institutions need the ability to define exceptions to the voucher number sequence.

Purpose: this will accommodate other electronic documentation numbers.

Acceptance criteria:

• Add toggle to voucher settings that when enabled allows the Voucher number to be edited by the user.
• This will replace the sequential number that was generated
• A prefix and starting number can be entered representing the first number to be generated
  • By default there will be no prefix and the 1st number in the sequence will be 1

Store value in mod-configuration. Coordinate this part with backend MODINVOICE-46.