mysql driver fix for non auto-increment primary key

Fixes issue when using non auto-increment primary key with the mysql driver and adds a corrected test for the issue.

Issue remains for sqlite. Fix for sqlite appears to be non-trivial as, unlike the mysql driver, a valid value of 1 is returned by sqlite driver for the last_row_id value. In order to determine if the last_row_id value should be applied, more details about the column definition are needed before line 151 of lib/Drivers/DML/sqlite.js in function Driver.prototype.insert. Without the column definition, I suspect any 'fix' would be more of a 'hack' than a fix.

I believe the mysql and sqlite drivers will both fail without column definition details in the case where a model has 2 primary keys with one of them being an auto-increment field. I will need to build a test case for this to be sure though.  A working test showing the issue for mysql and sqlite exists in in my repo in the file [test-multikey-auto-increment.js](https://github.com/esk525/node-orm2/blob/multikey_with_serialkey/test/integration/test-multikey-auto-increment.js).  This may very well be an edge case node-orm2 does not want to deal with.  If it does, one way to manage the issue without additional column details needed in the adapter is to require that the autoinc properties on created data not be set (so, in the adapter, they would be undefined).  The [mysql](https://github.com/esk525/node-orm2/blob/multikey_with_serialkey/lib/Drivers/DML/mysql.js) and [sqlite](https://github.com/esk525/node-orm2/blob/multikey_with_serialkey/lib/Drivers/DML/sqlite.js) adapters in that branch of my fork have been modified such that the returned ids hash returned by the adapter insert functions is more in line with the postgres adapter (they return a  hash of all key fields and not just the last insert id).  Just one option as an example.

Thanks.