Minor refactor
Use PVector to store beam position
Use PVector to store beam origin
Rename Distance.speed to velocity
Remove Beam.velocity definition
Set beam velocities in subclasses
Move velocity field to Beam parent class
Minor update
Rename Distance to BeamType
Change Distance occurrences to BeamType
Rename Distance to BeamType in NexusBeams
Minor BeamType update
Rename transparency to opacity
Fix #21: centre beams on mouse click origin
Merge pull request #22 from adeijosol/pvector

Resolve #20: use PVector to store beam values