Allow NSH date command with no RTC.  This command is useful without an RTC too.  Also, this permits testing on the simulator which never has an RTC

apps/modbus:  That completes a complete pass; all of the modbus files a little closer to NuttX coding style.  Still not compliant with naming conventions

Modbus: Change to more header files to make them a little more consistent with Nuttx coding stanards.  Still not very close

Modbus: Change to several header files to make them a little more consistent with Nuttx coding stanards.  Still not very close

drawline/drawLine should not take a boolean to select non lines caps or capping at both ends.  drawline/drawLine also needs to be able to put a line cap on one one end of a line

Add a 'capped' boolean parameter to all drawline/drawLine functions/methods.  The idea is that this will produce better joining between lines