(#597) #596
* Accept to specify a camera device with "-d /dev/v4l/*" in "/boot/octpi.txt"
* Support plug and play of a USB camera.
(delayed a read-link of a device link)
* Add feature: Load multiple camera configuration files.
* change video config file path to "/boot/octopi.conf.d/*.txt" and remove loading of conventional location video config file.
* Create video config directory and move config-file.
* Remove conventional config file
* Fix typo of variable name
* Fix typo of variable refernce
* Fix issue of raspi-cam with camera="auto" in webcamd script.
Change webcamd startup mechanism to systemd from init.d.