Implemented PlayDBPluginAdapter

PlayDBPluginAdapter is a Play plugin to use ScalikeJdbc with DBPlugin (and evolution).

There are several things to note.

* sbt name hashing option is commented out because running zentasks app causes an error. I'm not sure how to fix it.
* Dependencies and aggregations between projects are cleaned up.
* `zentasks` under `scalikejdbc-play-plugin/test/` and `scalikejdbc-play-dbplugin-adapter/test/` are almost identical except plugin setting and migration files. Is there better way than copy and paste to manage these?