Add ability to automatically resolve DB::connection('mysql::write') to use writable database connection as well as DB::connection('mysql::read') instead of adding duplicate connection config.

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch 'feature/connection-read-write' of https://github.com/crynobone/framework into crynobone-feature/connection-read-write
Cleaning up some code.