Genericize database methods; require result instead of masking lack thereof

This release is focused on a few pervasive issues in the DatabaseUtils class:

• Prior to this release, many methods returned Object instead of specifying a generic return type. This required client code to declare explicit type-cast operations and ignore the resulting "unchecked cast" warnings. These have all been updated to eliminate the need for these type-casts.
• If the specified query or stored procedure failed to return a result, the two getString(...) methods would return null and the two getInt(...) methods would return -1. In this release, failure to return a result for these methods will now cause IllegalStateException to be thrown.

I also added README references to a few neglected utility classes that I hope folks will find useful.