[connector:php] new volume options `encoding`, `locale`

for support non UTF-8 server

ref: Studio-42#443, Studio-42#446, Studio-42#466, Studio-42#570, Studio-42#601, Studio-42#701, Studio-42#911
Merge branch '2.1' into chrenc
[connector:php] refactoring about #937
[connector:php] on each function, locale of each volume is maintained
Merge pull request #937 from nao-pon/chrenc

[connector:php] new volume options `encoding`, `locale`
Merge branch '2.1' into 2.1_n