Added form field for number of records to process

Contributed by [got2code](http://vanillaforums.org/profile/45313/got2code)
Use LastIPAddress instead of UpdateIPAddress (more reliable)

Contributed by [got2code](http://vanillaforums.org/profile/45313/got2code)
Ignore records that have UserMeta information (like subscribing to discussions).

Contributed by [got2code](http://vanillaforums.org/profile/45313/got2code)
Deleted pre-existing cleanserlist
Cleaned up query
Minor readability tweaks
Do numeric id checking before performing delete action
Additional readability tweaks
Remove newlines from "About" text in created list
Use text input for number of blocks to offset, not drop-down for number of rows (which is inflexible)
Tweaked variable name for readability
Use SQL instead of query-building for flexibility and conciseness
Report number of users deleted after purge as status message
Added support for filtering by regular expression search, with preset to catch common spam