Some new functions and command-line switches

This pull-request covers 3 new functions, a new output format, and some supporting command-line switches:

 * subnet(ip-addr-field, ipv4-prefix-len, ipv6-prefix-len) --> masked ip-addr-field
   Applies a mask determined by the given ipv4 or ipv6 prefix (depending on address ip version) to an address.

 * istld(domain-label) --> true/false
   Given a list of current TLDs, true is returned if the given label matches an entry in the list.  The list is read from
   a file with location specified by the --tlds switch

 * isnewtld(domain-label) --> true/false
   Given a list of applied-for new TLDs, true is returned if the given label matches an entry in the list.  The list is
   read from a file with location specified by the --newtlds switch

 New switches:
   -i or  --tsv
      Return results as tab-separated values.

   -T or --tlds <file-path>
      Read TLDs from <file-path>

   -N or --newtlds <file-path>
      Read NewTLDs from <file-path>