Fix early init of logger without app classloader

The early init of the logger in dev mode now only
uses the default play logback configuration, and
doesn't attempt to use resources from the app.
The full configuration of the logger happens at
application loading.
Update the logger resource fallback file

If an explicitly configured logger.resource cannot
be found on the classpath, use the resource name
as a file in the application conf directory.
Merge pull request #3331 from pvlugter/logger-resource

Fixes for logger resource configuration in dev mode