API operation to insert new terms in vocabulary

[carueda]

Corresponding entry in old system: https://github.com/mmisw/mmiorr/issues/231

@mikebotts @jjfredericks @graybeal FYI

[carueda]

The addition of the new terms will not generate a new version of the corresponding vocabulary.

Regarding current vocabulary status the effect of adding terms is as follow (see also #36):

vocab status	new version?
draft	no
unstable	no
testing	no
stable	no
deprecated	no
archaic	no

[carueda]

Preliminary POST /ont/term in v3.2.1.

Adds a single new term. Parameters:

• vocUri: URI of ontology
• version: ontology version (optional)
• classUri: class of specific vocabulary (optional). If not given, and there's only one class in the ontology, then uses it. Otherwise, error.
• one of termName or termUri to indicate the URI for the new term (required)
• attributes: array of array of strings for the property values (required)

Example request for a vocabulary with only a class having one property:

$ http -a username:password post http://localhost:8081/api/v0/ont/term \
     vocUri=http://localhost:9001/src/app/~carueda/vocab1 \
     termName=baz attributes:='[ ["some prop value", "other value for same prop] ]'

[carueda]

Closing based on the already implemented operation. Open a new entry for any additional needed adjustments/fixes.