make YubikeyConfig a QObject and it's getter methods invokable

this will make the getter methods available for calling by name
through the meta object.
refactor building of the logging string

to use a lookup table and format-strings, calling methods in the
YubikeyConfig class by name instead. This will allow building more
flexible logging schemes.
localize OUT_CHAR_RATE defines to settingpage.cpp
move defines for accbox to yubiaccbox.cpp from common.h
change the radio buttons for logformat to a combobox
add a flexible logformat with configurable input
move help texts to it's own header

to reduce re-compile times due to changed texts..
add getting a list of lognames
add help for the flexible logging format