io.ascii - rework internals for Table support #307

io.ascii needs internal work to use the Table class natively (including metadata support). Part of this will be removing the MemoryReader which serves many of the same functions as the Table class.

Also, as a carry-over from an asciitable issue, from @hamogu:

• formatter and converter really do the same thing, one for input, one for output. That could be unified.
• Outputter as a class are only used when reading a table, maybe we should use the same structure for writing.

These are a lower priority but if there is code rework these ideas should be kept in mind.