MediaEncoderTaskPresetString and MediaProcessorsNames

I've added two new classes, 
* MediaEncoderTaskPresetString  
  Contains constants with the values of all available Task Preset Strings for the Windows Azure Media Encoder.
* MediaProcessorsNames  
  Contains constants with the names of the available Media Processors.

This classes were created with the objective of saving the time it takes to browse the Windows Azure Media Services documentation looking for an specific Task Preset or Media Processor.

Any feedback is more than welcomed :)