modified backup_table() so it accepts additional "old prefix" and "new prefix", to rename tables in generated SQL
added doc for backup_table()
new fields in admin to ask for old/new table prefixes, plus css for consistency
modified backup_db() so it accepts parameters for old/new prefixes, and changed the invocation to follow suit
sql comment headers now print the correct table name
bugs cleanup, and a bit more info in the sql header, and helper text in form