Refactoring: values are not stored with a full-prefixed name but arranged in
direct values/subtables pairs.
Added get_value function to get a tomlValue from a table and a key
(or fail if entrie at "key" is a table).
Added code coverage rule (using bisect).
Added failing test for value using same key in different tables.
Fixed "same key/diffent group" issue.
Added get_table/value failure test.
Added note about array of tables tpe which is not supported.
Fixed print (moving string_of_list from mutually recursive to out of it)
Added test file from official TOML repository.