copy_to() works for src_oracle
Removed sql_create_temp() generics because turns out they aren't needed for Oracle (temp tables in Oracle have a diff syntax than what's used in DPLYR already, but temp tables are not temp to a session, just the data inserted in them).
lahman_oracle(): now uses 'lahman' user by default. src_oracle(): no uses localhost as default
added sql_subquery.default generic to allow tests to pass