Remade README.table.rst to README.table.md

All other README and documentations in this project is in markdown
format. It make sense to change this file to markdown too.

Also removed all number words from the file to make it easier to
change..
Added documentation line for the new table.txt field

Added the description for the new "simplified variant" field.
Added simpchar to cangjiechar (API break)

This commit added "simplified variant" field result into a new
struct field simpchar in cangjiechar. SQL queries are updated to
query and pass the data correctly.

TODO: modify the CLI tool to test the query result
Updated CLI to output the new simpchar field

Updated CLI to output the new simplified variant field. Users may
examine the results with CLI.