Oracle: Should allow users to have a different user between runtime and design time

[colinbull]

A common enterprise scenario, is having the same schema under different users to separate environments, for example development might be HR_DEV and test might be HR_TEST currently the schema owner is statically compiled, which prevents users with this configuration using the provider.

This is quite a big change on a par with #87. In fact probably touches most of the same code.