Moderate new members 1.6

Moderate new members v1.6 changes:

Added to options page a "Exclude user groups" selection.

Moderate new members v1.5 changes:

Fixed issue where null condition caused server error.

Moderate new members v1.4 changes:

Fixed issue with approval queue not showing for moderated threads.

Moderate new members v1.3 changes:

Fixed issue where Approved threads and Approved posts setting count.

Moderate new members v.12 changes:

Fixed issue with last post information.

Moderate new members v1.1 changes:

Updated PHP code so that only new posts and new threads trigger the moderation check.