List example entries on admin/config pages

Currently, someone who is not savvy enough or has not set up metatags before may have trouble deducing what the following actually means without trial and error:

If you need to define any static Metatags for this type, enter them here in the form <name>|<value>, one per line. You may also use any of the currently supported tokens found in the "Available Tokens" fieldset below (e.g. [author-name]).

Please consider including one or two explicit examples such as:

Consider also clarifying that when listing more than one entry of the same type (such as the keywords lines above) they will automatically join together in a standard comma-separated format.

All of this should be generally obvious, but people new to web dev could use the extra info.

Thanks for the great module!