Alias knockout -> k.o.

BUR #26316 is pending approval.

create alias knockout -> k.o.
create alias knock_out -> k.o.
category knock_out -> general

Essentially two tags for the exact same thing ("knockout" is usually shortened to K.O.). Also added spaced alias just in case.

topic #19893
knockout Post History
knock_out Post History

There doesn't seem to be a need for aliases. Fix isolated errors manually. If necessary, make tags (without a wiki) ambiguous.