Loan/ Deposit Letters; not locking Letter and Status fields when log is Read-Only

When editing Loan or Deposit Letters, and the log is Read-Only the Letter and Status fields may still be able to be changed (depending on its status). When saving the changes finPOWER will fail with an error message (the correct behaviour).

There are two main reasons why the Log may be Read-Only:

1. The database is Read-Only.
2. The User does not have sufficient permissions, eg LoanLogUpdateAny is denied.