add option to enable linewrap mode

re-enable line wrapping for the input line (previously dubbed 'WORD-wrapping' - incorrectly)

as per Tucos's comment on IRC ('iirc it didn't actually break anything, but the big boss was hesitant to just add it back in without proper testing'), this has been built on linux x86/x86_64 platforms with Qt 4.8.4/5 and 5.1.0 and used without issue for a day, so hopefully isn't going to be too problematic