Collection specific plugins

Some notes on adding collection-specific plugins and macros.

Plugins go into collect/colname/perllib/plugins

Macros go into collect/colname/macros

other collections can still use the standard ones.
 * 1) It's best to put modified plugins into collect/colname/perllib/plugins, so any
 * 1) A collection specific plugin has to have the same name as an existing plugin if you are over-riding the system-wide version of the plugin.
 * 2) The collection-specific one is used instead the system-wide one.
 * 3) The 'collection specific' plugin appears in the gli when you have that collection loaded.

Collection specific macro files go into collect/colname/macros, and are used instead of the system ones.

Thanks to Wendy Osborn for most of this text.