Changes

* # USPTO historical assignment data *#* The issue with table keys is potentially resolved.*#* Create a table to enable us to track patent ownership through the life of a patent. * # Assignees data*#* Identify U.S. assignees in the data for all assignees without a valid country or state entry. * # Maintenance fee data*#* Create a table with all the active patents and their expected remaining life using the maintenance fee event codes.* # Citation data*#* We need to recognize patterns in the cited patent numbers. A low hanging fruit would be to match all the publication numbers to the granted patent numbers in the histpatent table. Few other repeating patterns seem to point to foreign issued patents.