Added new code for upper/lower case disambiguation.

Several jobtitles depend on whether they are capitalized or all lower case.
Some are titles only if lower case: e.g., potter.
Some are titles only if upper case: e.g., General.
Some titles have different occ codes depending on their case: e.g., President, president
All these ambiguous titles are now identified in jobs.json as negative numbers which triggers jobs.py to check for capitalization.