Oracle DSN string fix

Modified DSN string to conform to PDO Oracle requirements
[update] Code optimization
[update] Code reorganized
[feature] LIKE statement with operator as value condition #155
[feature] Add support for unix_socket connection
[feature] Improve logging feature and add log() API for #166
[feature] Add alias for joining table to support joining the same table with different column
[fix] Fix typo
[feature] Add table joining support for get API
[fix] Fix get API bug
[fix] HAVING clause error
[fix] Table joining with alias bug
[update] Improve and optimize database connection
[update] Update composer.json
[update] Add Medoo logo
[update] Update Readme.md
[release] Medoo 0.9.7