- relative application of stencil by passing in field accesses
- documentation + doctest

- support aligned load/stores
- nontemporal stores
- aligned memory allocation for arrays and temporary buffers

- Previously sympy.Eq was used to represent assignments. However Eq
  represents equality not assignment. This means that sometimes sympy
  "simplified" an equation like a = a  to True,
-> replaced sp.Eq by pystencils.Assignment everywhere
- renamed EquationCollection to AssignmentCollection