Commands associated with a transaction object are executed as a single transaction. The transaction is terminated with the
ULTransaction.Commit or ULTransaction.Rollback methods.
The transaction is created with the IsolationLevel.ReadCommitted value.
To associate a command with a transaction object, use the ULCommand.Transaction property. The current transaction is automatically
associated to commands created by the ULConnection.CreateCommand method.
By default, the connection does not use transactions and all commands are automatically committed as they are executed. Once
the current transaction is committed or rolled back, the connection reverts to auto commit mode and the previous isolation
level until the next call to BeginTransaction method.
UltraLite's definition of each isolation level is slightly different than ADO.NET's documentation of IsolationLevel.
This is the strongly-typed version of the System.Data.IDbConnection.BeginTransaction and System.Data.Common.DbConnection.BeginTransaction()