experDesign 0.4.0

• Check that index used in inspect() has a valid length, positions and
  replications matching the data provided.

• check_data() gains a new omit argument (#49).
  If you relied on positional arguments it will break your scripts.

• Omitting non existing columns now creates a warning.

• Now it is possible to remove full rows or columns from spatial(): like remove_positions = "A" (#52).

• Fix a bug in spatial() that in some cases assigned multiple samples to the same position (#51).

• Spatial indexes are returned in row, column order: A1, A2, A3, ... A10, B1,.

• Function position_name() is now exported to facilitate generating designs.