Change all logging calls so they don't format strings

Currently all logging calls in FSLeyes (and associated projects) call .format on the log string, e.g.:

log.debug('format this string: {} {} {}'.format('a', 'b', 'c'))

But the logging module can do string formatting for us:

log.debug('format this string: {} {} {}', 'a', 'b', 'c')

If you switch over to this convention, it will mean that there does not have to be a (large) performance penalty to leaving log calls in the code.