Added support for trajectories, read them in using XYZ

This just reads in simple XYZ trajectories, and adds support for
storing multiple 3D coordinates.

Change-Id: Iaee31b121a2a9a6a4f6bc5a97f8ab712832b23ab
Added support for transparent rendering in VTK

Change-Id: Icf9e1dcb2d17f8da55f000a7db67010633690bc6
Added a simple animation tool for trajectories

Change-Id: I1dc9727a2591faeb55b2fdadc576ff3fda66c106
Merge branch 'trajectories'

Change-Id: I4ec643e60dd1ea3e11956457f35691d5ef12f7ba