Namespace the commands

[Andrus Adamchik]

Liquibase module contributes 5 commands already and will contribute 6th per #15 shortly. This can be confusing in an app that contains Jetty and other commands, as some commands have pretty generic names (like "update" or "validate"). I think we must prefix all of their long names with "lb":

--lb-update
--lb-validate
--lb-changelog-sync
etc...

Short names should be preserved for partial backwards compatibility.