Reduce memory usage when running a command.

Each time you run a command from the command shell, the system uses around 80Kbyte; try running "memory" a few times.

This needs to be reduced.

(My first guess is that most of the memory is being used is being consumed by the new thread / thread stack that is allocated each time a command is run. If so, we could modify the invokers to recycle threads when commands complete.)