Make SQL method semantics consistent

[mitalia]

In general we have a mix of semantics in use when sql methods are called. They should be unified as follows:

If a method can return something (e.g. a count, resultset, etc...) it should return an Option[Type]. If the method merely performs a task which may or may not succeed, it should not return anything and should instead rely on exceptions for proper error handling. In cases where the underlying JDBC driver returns some true/false that must be checked, this should be promoted to a try/catch exception mechanism.