Add :use uninstall feature.
Modified the plugin/dependency commands for Gremlin Console.

Got rid of :use - replaced with :install :uninstall :plugin.
Refactoring around PluggedIn.

PluggedIn now holds the groovysh and io instance.
Move string path to member variable to be more reusable.
Add default plugins.txt file that includes server and utilities.
Allow cleanup of plugins.txt file if a plugin was active and then ":uninstall" executed while still active.
Merge remote-tracking branch 'origin/master'
Remove reference to modern graph.
add sugar to plugin list so serviceloader can find it
Update docs around new form of :use as :install :uninstall :plugin.
get rid of reference to modern graph in gremlin-server-min.yaml.
Fix the list command to show the plugin name.
Allow the plugin to be looked up by name when using :remote.
Remove remaining references to modern toy graph.
Merge remote-tracking branch 'origin/master'