add more column specs

[yangg]

• add option timezone for datatype timestamp and time
• add datatype json & jsonb (disable warning)
• add option comment(work with exec extra callbacks after create table(or add column) db-migrate-base#6 which exec extra callbacks after create table)

[wzrdtales]

sry for the long delay going to merge this.

[wzrdtales]

Merged in 401ac2d