Add default system-wide plugin location to facilitate packaged installs

[jfkw]

To improve options for packagers, please consider adding a default system-wide location e.g. /usr/share/octosql/plugins as the first path searched for installed plugins. The user's ~/.octosql/plugins/core/ would be searched next and plugins to be loaded would be the combined set.

I am packaging OctoSQL for openSUSE and would like to build and package the standard plugins for system-wide install and package management without requiring internet access.

[cube2222]

You can change the plugin directory from ~/.octosql/plugins to a different one using the OCTOSQL_PLUGIN_DIR environment variable.

Would that be enough for that use case?

If it's not, I'm happy to add what you proposed.