Reinstate searchsorted()

* Returns the range of indices in a sorted array equal to a given value
* Returns an empty range located at the insert location if the value is not
  in the array
Merge pull request #2977 from kmsquire/searchsorted

Reinstate searchsorted(), returning a range
remove redundent tests introduced by 6f814674a50fcfdd2c9c69743581b3f00e323020