Command-line switches & beaglebone (and maybe other boards) support

The "open by bus name" feature is nice, but it breaks on BeagleBone because it has spaces in it:
# cat /sys/class/i2c-dev/i2c-1/name 
OMAP I2C adapter

# ./hyt-read OMAP I2C adapter
usage: ./hyt-read [ i2c bus name ] [ slave address ]

# ./hyt-read "OMAP I2C adapter"
could not find i2c bus OMAP I2C adapter

so I modified the code to allow direct /dev/i2c-X access and some other features.