I need to be sure that numpy lets `FunctionalUnit` take precedence over `Quantity`. Obviously, I could also increase its `__array_priority__`, but it seemed more logical to use the thousands for all units stuff.

Similarly, in `__mul__` and `__div__` below, I need to ensure that `q * lq` gets given to `lq.__rmul__` (here, multiplication and division are particularly important.

Though this actually may not be best: it really should break in the multiplication of the units. Need another test case...