Add `&AlreadyInUSKP` predefined message.

The "Delete. Already included in Unofficial Skyrim Patch.esp." message
is used 140 times throughout the current masterlist. Moving it to a
predefined message reduces both the number of lines in the masterlist as
well as hopefully making maintenance of it more manageable.
Fix Spanish text in `kerplunk.esp`'s msg.

The Spanish text was referencing "Unofficial Skyrim Patch.esp" while the
`condition` of the `msg` was checking for "WATER.esp".
Fix pseudo-req for `CiviliansWillNotDiePatches.esp - CWND-UnofficialPatches.esp`.

It used a `msg` to inform about requiring the USKP instead of simply
using a `req` list.