SQLite: pragma and transaction

[dimasagalov]

While working with a bunch of libiec61850 + SQLite3, I ran into the problem that SQLite3 has very low performance with the settings out of the box (individual synchronous inserts, each ~20ms). And there is no way to customize db.
My suggestion is to expand the interface:

1. introduce a function 'SqliteLogStorage_createInstance_ext' with argument through which you can pass pragmas before creating the db instance.
2. introduce a function 'SqliteLogStorage_exec' (wrapper for sqlite3_exec) through which direct SQL queries can be passed. In particular, through them, you can create a transaction that stores all statements in the cache and runs them when the transaction ends - which is much more productive than individual inserts. The transaction begins after locking the data model and ends before unlocking it.
   In attach - possible implementation approach
   sqlite_pragma_and_transaction.zip