Code cleanup for ItemFactory

Getting rid of old code that isn't needed anymore. Added E-Tank to item
templates.
Improved AudioService use via CommandProcessor

Now its possible to play music and samples through the console.
Added audio playback for game play state

Need to change this so we can obtain a MusicId from the level and play
that, but the code to "do" it is in the right places.
Commented out some debug code to clean up log

The console is getting flooded with jumping ascending/descending
information that isn't important to know about right now. Commenting it
out until it is needed again later.
Replaced 1-frame duration calculation with value

Using a constant to represent 1 frame's worth of time instead of
calculating on the fly. No gains except for readability's sake.
Exposed audio system to script via proxy class

A new proxy class, AudioServiceScriptProxy, exposes an instance of
AudioService as a set of static methods. This allows easy binding of the
static methods to the script layer without having to bind the
AudioService class directly, and avoids weird construction issues with
Sqrat. If no AudioService is set then the methods do nothing, so the
scripts still work fine.
Merge pull request #52 from zackthehuman/master

Audio improvements, exposed audio to scripting layer