Bunch o' changes

Too many changes (I'm sorry we didn't open PRs along the way):
- Add row prefetch environment variables (so that we can optionally fetch more than one row). Consider moving this to DSN parameters now that these exist?
- New DSN parsing that allows for parameters after ? (similar to other drivers)
- Handle nulls when reading and writing to Oracle
- Handle truncated strings from Oracle
- Fix indp data type to be a C type
- Handle DATE columns in Oracle when reading and writing
- Allow specification of timezone as 'loc' parameter (similar to go-sql-driver/mysql) that will be used to read times as from the DB and to marshal times to when writing to the DB for date fields with no timezone info