Improved Radio Pulsar Search graphics

* Refactored code to increase CPU efficiency
* Alpha blending is turned off while power spectrum is rendered (see below)
* Optional smoothing is turned off while power spectrum is rendered (crisp lines!)
* Moved fixed values to variables, decreased real-time computations
* Added threshold to show candidates in more prominent color
* Power spectrum label now mentions Arecibo as data source
* Fixed glLineWidth/glPointSize invocations (outside glBegin/glEnd!)
* Fixed color values
* Pending: how to deactivate alpha blending for individual parts of the spectrum?
* Pending: add semi-transparent backdrop to power spectrum when alpha blending control works