Move DBAppender SQL scripts from src/main/java to src/main/resources

Putting those scripts in logback jars allows to use them while testing your code with an in-memory database like this:

`jdbc:h2:mem:test;DB_CLOSE_DELAY=-1;INIT=RUNSCRIPT FROM 'classpath:ch/qos/logback/classic/db/script/h2.sql'`