Create a new node tool supporting force compaction of a partition

Need to create new tool called nodetool forcecompact. The syntax of the command is
nodetool forcecompact keyspace table <list of partition keys ignoring the gc_grace_seconds>.

One of the use cases of the tool is to handle the bad partitions which may contain too many tombstones. The tool will compact all the sstables containing the partition keys. In addition, by ignoring the gc_grace_seconds, it will help purge the tombstones faster.