Remove all actions after turning persist off

[RoyCurtis]

This is a duplicate of my pull request to the original LWC repository

Common source of confusion for players using persist mode; there may still be a lingering action (e.g. /lock) after turning persist off. Eventually, they may accidentally apply that action.

Example

1. Player executes /lwc mode persist to turn on persist mode
2. Player executes /lock and begins punching many chests to mass lock them
3. Player executes /lwc mode persist to turn off persist mode
4. Later, player punches a lockable item (e.g. sign or chest) and accidentally locks it, because of lingering lock action

Notes

• This change was made via GitHub's file edit interface; therefore it has not been tested for compilation or runtime errors
  • To ensure I used the correct behaviour, I used DropTransferModule.java and line 1927 of LWC.java for reference
• This suggestion arose after repeated confusion and accidents on our server. I also think this is more convenient behaviour (wouldn't turning persist mode off signal the end of one's mass-locking, for example?)

[dmulloy2]

I'll add Travis testing when I get the chance, but that would appear to be a valid call. Thanks again!