remove multimon/span logic from cmdline.c and move to new combined logic...

Re-write of https://github.com/FreeRDP/FreeRDP/pull/1976 for new cmdline/rdp file combined logic: 

Move multimon/span logic from 'cmdline.c' to 'client.c' in the new combined_logic section.  

As a result of this now matching behavior, FreeRPD aligns with the behavior of M$ when opening RDWeb connections via RDP file. (RDWeb's generated rdp files have multimon set to TRUE, but do not specify any screen geometry, because multimon is supposed to imply fullscreen).