allow multiple firetowers per working directory

[mweitzel]

allow multiple firetowers per directory, with optional name

• firetower -n 'command' always creates a new process host with a unique name
• firetower -n name 'command' creates a new process host if name is unique
• firetower 'command' creates a new process host if none exist already
• firetower -r resets all
• firetower -r name resets only matching name
• process hosts display their name