Extended errors

[zauguin]

Expose extended result codes from SQLite.

The list was moved into a macro based separate file to avoid duplication the list, which seemed error-prone, especially since the extended code list might chnage more often.

[aminroosta]

@zauguin This is just a suggestion, can you move sqlite::exceptions namespaces and all the macro stuff into another header (exceptions.h).

besides that as always great work, well done 👍, we just need a unit test and updated readme :-)

[zauguin]

@aminroosta I moved it into a errors.h header und renamed the exceptions namespace to represent the more general usage of this classes in preparation for #109. The old named is preserved in form of an alias.
Maybe sqlite_exception should be renamed too?

[aminroosta]

@zauguin renaming sqlite_exception will be backwards incompatible, so let's just keep it :-)

This PR is perfect to me, the readme & tests are all great 👍
I'm merging it, we will have another PR for #109