Enable install of apps before startup of ZLUX app server

[markjhollands]

Currently, the apps / plugins are extracted to a shared volume that the ZLUX app server container can see, however these apps are not automatically installed before the ZLUX app server starts.

There are two issues with this:

1. Required plugins are not there on startup, for example ZSS auth
2. A user is required to log onto the container to install the plugins, which is potentially a security risk

These plugins need to be installed before the main ZLUX app server container starts

[markjhollands]

Added a new script as per PR #12. Plugins that have been extracted to /dropins are now automatically installed on start up.