Allow apps to be configured in individual files

The current model for application.yml is that it contains all the configs for all the individual applications. This makes it complicated to do automatic deployments with, say, ansible as one needs to go and find the blocks in application.yml and make changes / additions. It would make automated deployment (ansible, or via continuous integration like Travis) a lot easier if there was a way to tell shiny proxy "read all files in directory ./apps.d and use their configuration as if it was part of application.yml. This could be either default behaviour or could be triggered through an Include directive or similar.

This behaviour of reading all configuration files as snippets from a directory is very typical for many servers (e.g. nginx, dnsmasq, rsyslogd etc), and would be very helpful.