rewrote serial parsing, added rgbw command to set all four levels

Serial parsing was inadequate for my requirements: there was no way to set all levels simultaneously, multiple commands sent together would result in all except one command being dropped, and commands were being misinterpreted (ie, goblue could be read as a Blue: 0% command)

All commands are now delimited by CR, LR, or both, and should look like "red123" (no parentheses as shown in the manual)

Also added an rgbw command that takes three digits for each level, 000-255.  For instance:

rgbw111222123045

sets red=111, green=222, blue=123, and white=045.