Normalizes people in package.json.

author and contributors fields are normalized to objects per the description
here: https://npmjs.org/doc/json.html#people-fields-author-contributors
validates brackets.engine
adds file for test in previous commit.
Allows the rejection of certain words in package.json name, title and description fields.

Also adds the new validation strings.
Merge pull request #3384 from adobe/dangoor/more-validation

Adds additional validation used primarily in brackets-registry