Added support for custom plugins in dir outside sofine project tree. So users can have separate dir, tests, repo and deploy path for their plugin library. Requires single plugin.conf file in project root with JSON entry defining 'plugin_path'.
Renamed plugin.conf to example.plugin.conf since users should supply their own and this is just an example.
Added guard to not throw or use custom plugin path if plugin path not created and configured. Renamed existing example conf to example.plugin.conf and made conf.py look for an example.plugin.conf and then a plugin.conf and not throw if neither found.