core: Fix timestamps in manual /away messages

core: Fix timestamps in manual /away messages

Change handleAway() to NOT skip timestamp formatting by default.
This is the intended behavior as the one situation where it should be
skipped already manually sets skipFormatting to true.  All other
places deal with unformatted input strings (either from identity or
set by the client).

Remove now-redundant call to formatCurrentDateTimeInString() as the
handleAway command now uses it by default.

Fixes sending "/away Away since %%hh:mm%% on %%dd.MM%%" on the client
not getting formatted as "Away since 07:43 on 22.10" or some such.

Resolves GH-288.