#149 add slot value assignment to find/annotate

[Helen-Johnson]

It would be useful to be able to use the find/annotate function
to not only assign a class but also provide slot value information
for found-spans.

Example:
Say that in the ontology the class "protein" has slots "UniProtID" and "TaxonID".

Using find/annotate, search for string "p53".
Assign the class "protein" to found-spans.
Also assign the value "P04637" to the UniProtID slot,
and "9606" to the TaxonID slot.