#15 : Added skeleton of barrel module code.

Also added TestBarrel module for testing later. Barrel modules cannot
currently be used for anything.
#15 : Added barrel slot to gun bench GUI display.

Updated the positions of the existing slots to match. There is currently
no actual slot in the position indicated on the texture, but the
rendering is set up.
#15 : Added barrels to Gun Bench and related code.

User can set a barrel for their gun. Currently this is not saved into
the NBT tag and all guns are assumed to contain a TestBarrel.
#15 : Correctly store the barrel in the NBT tag.
#15 : Added barrel to FireEvent.

This allows shot handlers to pattern match based on barrel. Not
currently used yet as the two barrels are not yet implemented.
#15 : Replaced TestBarrel with BeamBarrel and BlasterBarrel.

Also updated the localization strings to include the barrels, and
incorporate them into the generated description string.
#15 : Implemented bolt/beam switch based on barrel.

Also separated precise shot handler into a separate ShotModifier.
#15 : Added NEI item set for Barrels.
#15 : Removed Precise Beam Lens.
#15 : Added temporary recipes for Beam/BlasterBarrel.
#15 : Minor tweaks to raygun name generation.
#15 : Disallow the death ray + scatter lens combo.
#15 : Moved spawning of Beams to the server.

Not sure why it wasn't there already. Also fixed the resulting rendering
glitches.
#15 : Fixed pitch/yaw of scatter beams all being the same.
#15 : Fixed impact particles spawned by beam shots.
#15 : Fixed rendering of Lightning beams.
Finish barrel-module. fixes #15