nutconf: bugfixes + HTML manpage
nutconf: device with no options bugfix
nutconf: proper device config dump
nutconf: another round of bugfixes

--{get|set}-mode options have replaced --mode option
--set-mode option actually sets the mode in nut.conf
libnutscan provides devices list rewinded (i.e. handled by the head)
libnutscan options fixed (so that the 1st is dynamic, too)
libnutscan: serial device type string undefined
libnutscan: dev. type strings array size fixed
nutconf: --scan-serial port list bugfix

Piggybacking: added device type check to skip invalid
devices returned from libnutscan