Add hooks for `script` command

[tohagan-tmr]

I found that when using this setting in development.properties ...

hook_after_each_up=SQL:after-each-up.sql
hook_after_each_down=SQL:after-each-down.sql

The SQL in after-each-up.sql and after-each-down.sql was correctly executed when running migrate up and migrate down but was excluded from code emitted by migrate script.

I'd recommend this feature be added and enabled via an option in .*properties files such as hook_sql_scripts_enabled=true which would be false by default for backward compatibility in case existing projects don't wish / expect this to code be emitted. I think it's reasonable to assume that non-SQL hooks are always ignored.

[harawata]

Hello @tohagan-tmr ,

#199 seems like a good use case for this enhancement (i.e. append COMMIT call after inserting changelog entry).
The implementation will be significantly different from the existing hooks, so give me some time to think about it.