Fix line wrapping for long options

The default line length for console output should only be set in
HelpWriterContext::writeTextBlock(), but not in the lower-level helpers,
which are generally called from contexts where line wrapping is getting
done on a higher level.

For example, 'gmx help hbond' shows some extra line breaks in the long
option descriptions without this fix.

Also removed an unused overload, that would also violate the above principle.

Change-Id: Ia40cea399c0f0f95d6d53ca2872d93baba47844e