tests for transaction RAII behaviour, transaction documentation, minor doc fixes

src/base.cpp

@@ -216,6 +216,14 @@ void LMDBAL::Base::drop() {
 /**
  * \brief Begins read-only transaction
  *
+ * This is the legitimate way to retrieve LMDBAL::Transaction.
+ * LMDBAL::Transaction is considered runnig right after creation by this method.
+ * You can terminate transaction manually calling LMDBAL::Transaction::terminate
+ * but it's not required, because transaction will be terminated automatically
+ * (if it was not terminated manually) upon the call of the destructor.
+ *
+ * You can not use termitated transaction any more.
+ *
  * \returns read-only transaction
  *
  * \exception LMDBAL::Closed    - thrown if the database is closed
@@ -229,6 +237,16 @@ LMDBAL::Transaction LMDBAL::Base::beginReadOnlyTransaction() const {
 /**
  * \brief Begins writable transaction
  *
+ * This is the legitimate way to retrieve LMDBAL::WriteTransaction.
+ * LMDBAL::WriteTransaction is considered runnig right after creation by this method.
+ * You can commit all the changes made by this transaction calling LMDBAL::WriteTransaction::commit.
+ * You can cancel any changes made bu this transaction calling LMDBAL::WriteTransaction::abort
+ * (or LMDBAL::Transaction::terminate which LMDBAL::WriteTransaction inherits),
+ * but it's not required, because transaction will be aborted automatically
+ * (if it was not terminated (committed <b>OR</b> aborted) manually) upon the call of the destructor.
+ *
+ * You can not use termitated transaction any more.
+ *
  * \returns writable transaction
  *
  * \exception LMDBAL::Closed    - thrown if the database is closed