Temporal interpolation replaces flow, bug fixes

This release includes some important bug fixes along with a few documentation updates and some minor quality of life improvements. Highlights are:

• Important corrections to the equations for inertial particles and massive particles with drag
• Some cleaning up of vtk import methods
• Important bug fix for temporally varying fluid velocities and the extend environment method
• Adds a method for calculating the material derivative
• Vicsek example updates