Write unit tests

[mochell]

Write a set of unit tests that execute on a regular basis:

• fetch relations
• Structures and Architectures
• PIC algorithm
• Lagrabgien 1D and 2D
• PiCLES 1D
• PiCLES 2D
  • Periodic
  • non-periodic
• initialization, run, reinitialization
• Saving procedures