Handle different charsets

[nerai]

Currently, the library assumes ASCII at all times. (I hope I did not miss anything.) Out of interest, I just checked and KGS seems to store SGFs in UTF8.

It misses the CA property of the SGF standard.

Property:	CA
Propvalue:	simpletext
Propertytype:	root
Function:	Provides the used charset for SimpleText and Text type.
		Default value is 'ISO-8859-1' aka 'Latin1'.
		Only charset names (or their aliases) as specified in RFC 1345
		(or updates thereof) are allowed.
		Basically this field uses the same names as MIME messages in
		their 'charset=' field (in Content-Type).
		RFC's can be obtained via FTP from DS.INTERNIC.NET,
		NIS.NSF.NET, WUARCHIVE.WUSTL.EDU, SRC.DOC.IC.AC.UK
		or FTP.IMAG.FR.

I am currently working on this issue for another project. If I find the time I will create a PR.

[paviad]

I'd appreciate it, thanks!

[nerai]

To state the obvious: I've not come around to work on this and probably will not in the foreseeable future. Sorry about that. It's up for grabs