This enables use of encrypted databases if LuaDBI or LuaSQLite3 has been
linked against SQLCipher. Using `LD_PRELOAD` may work as well.
Requires SQLCipher >= 4.0.0 due to the use of UPSERT
The :execute method is mainly used for one-off queries such as creating
tables and indices. There is no need to cache this prepared statement,
as those queries are only done on startup.
Further, prepared statements can't be reused without being reset, so
this was likely broken anyway.
There were 3 very similar methods:
- :execute()
- :execute_query()
- :execute_update()
The first one returns the prepared statement and is mainly used
internally in the library for CREATE statements.
The later two only really differ in how the results are returned.
Those two are one main method and one small one that only picks out the
iterator.
