gs2: no need for a third copy of the usage info

The manpage and the --help text is more useful than a comment.
gs2: split --verbose and --debug again

--debug prints all Modbus messages, which is a lot.

I want to use --verbose to print more terse information in a coming
commit.
gs2: let the user specify accel/decel config on command line

This adds a couple of new command-line arguments that lets the user
specify the acceleration and decelerataion time of the VFD (time to go
from 0 to Max RPM, and from Max RPM to 0).  If no command-line arguments
are given, it behaves like before (10 seconds to accelerate, coast to a
stop without control).

This also adds a command-line argument to enable better use of a braking
resistor.
gs2: update copyright