Removed unnecessary double-encoding of swing values in die table

Currently, we save the swing values of dice into both the die table and the game_swing_map table.

This pull request removes the swing_value column from die, and all the code that refers to it. All functionality with respect to swing values should remain unchanged.

This is preparing the code for the caching of the previous round's swing values in a new database table. 

Requires database update swing_double_encoding_001.sql.

http://jenkins.buttonweavers.com:8080/job/buttonmen-blackshadowshade/161/