First, be more explicit when we mean a range of values in a field or a
spacial bounds. Use the Range and Bounds structs in Field and
CoordinateSystem to make all of this more clear (and reduce a bit of
code as well).
These asserts are consolidated into the unified Assert.h. Also made some
minor edits to add asserts where appropriate and a little bit of
reconfiguring as found.
There was an inconsistency in naming classes where axes-aligned grids
with even spacing were sometimes called "uniform" and sometimes called
"regular". Maintain consistency by always calling them uniform.
