Speakers

Added speaker assemblies
They have to be used in conjunction with other assemblies (proximity sensors, signallers, etc)
They yell out pre-defined messages when activated (messages can of course be changed)
They can be renamed with a pen
![selection_024](https://cloud.githubusercontent.com/assets/7786335/3562314/cb13c398-09e9-11e4-8785-c5803eed8e96.png)