Adding --force-named-panic option

[shlomi-noach]

When --force-named-panic is given, a panic command must also indicate the name of migrated table, or else it is ignored.
This can be useful in mass-distributing a panic request to potentially multiple gh-ost migrations, when in fact only seeking to terminate a specific migration.

[shlomi-noach]

This PR also supports non-forced named throttle. i.e. you may for example echo throttle table_name | socat - /tmp/gh-ost.sock, and the migration will only throttle on a table name match.