MD2 & WAVE fixes, OZ_PULSE_BELL

- ozCore
  * PulseAudio backend for System::bell() is optional, enabled by OZ_PULSE_BELL
- ozEngine
  * WAVE loader fixed for files with additional data chunks
- client
  * MD2 weapons are transformed by default by weaponTransf, untransformed when
    rendered on bots
  * Shader::Mode (SCENE, UI) removed, unneccessary because of ModelField
UI sounds, fixes

- matrix
  * Synapse fixed to use orbis.obj() etc.
- ui
  * UI sounds for button clicks, inventory actions, next vehicle weapon ...
  * UI sounds are configurabe in Style
- client
  * Context::playSound()
- builder
  * -e to build terra & BSP textures
  * -R to skip reference checking
  * sounds referenced by UI style copied