Add ODBC driver

[moteus]

I write ODBC driver for DBI library based on my Lua-ODBC library.
I slitly change tests:

1. I use select cast(? as <TYPE>) as retval to test type encodings.
2. I found that ODBC drivers for MySQL/PgSQL does not get any error when call prepare with invalid SQL. So I also try call execute.
3. I do not call test for returning id because MySQL does not support it.

For now I add DBI.lua to my repo because I want run tests on Travis. But I will not add this to luarocks.
I add it only after you change main luadbi module so it can load ODBC driver. So i can just add luadbi as deps to my module.

PS.
I also add some tests to fetch, close, tostring and execute same statement with different query multiple times

[sparked435]

DBI.lua now checks for driver 'ODBC' as dbdodbc as well.

[moteus]

Just tested my ODBC driver with v0.6.
All works. Add module to luarocks.