Improved commander go, halt.
Improved commander go, halt.

- go command prints more accurate information about the resulting target
  state, mostly importantly no longer reporting failure if the device
  just entered sleep, as Mbed OS apps often do.
- halt command reports the resulting target state if it's not halted.
- Added 'continue', 'c' aliases for go command to match gdb.

flit/pyOCD,mbedmicro/pyOCD,mbedmicro/pyOCD,mesheven/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mesheven/pyOCD,pyocd/pyOCD,pyocd/pyOCD,mesheven/pyOCD