Fix 'native_database_types' data in adapters

These are apparently not used for anything (even though @hpainter
changed the values to fix something in 21b604ad487f0507bb86c5ac25be2d04b0f4e7d3
:confused:).

The "native_database_types" now match up with the Rails implementation
and also fix some of the pgsql types that weren't right.
Merge pull request #12 from getloaded/fix-adapter-native-database-types

Fix 'native_database_types' data in adapters