Adaptated the bundle to allow fine-tuning without altering bundle files.
- DB tables names can be configured in a configuration file
- Migrations have been updated to be configurable: they use the dynamic tables names and details of tables structures are externalized in a subdirectory that can be overwritten through the configuration file
- Client migration name has been changed so that it's the first to be executed. As clients table is referenced by others, it allows developer to add foreign keys constraints on client_id columns
- A .gitignore file has been added to ignore customizable elements: configuration file, custom migration details and classes overwritten by developer
Documentation has been updated accordingly.

If no specific configuration is applied, database structure will be the same as before, with a few exceptions:
- client_secret has been set to 60 chars length in the clients tables: no need more, as the hashes generated by the bundle are that length.
- redirect_uri length was sometimes 200, sometimes 255. It has been harmonized to 255.
- scope length has been enlarged to 255
Re-integration of a hard length limit for client ids, but enlarged to 255 chars.
Fixed documentation error