Support 8-bit encoded strings

[GoogleCodeExporter]

Java's default UTF-16, 2-bytes-per-character string encoding, is inefficient 
for strings which otherwise could be encoded with a single byte per character.

It should be possible to represent characters in the trees using only a single 
byte per character, when working with compatible strings. This may reduce 
memory overhead by 50%.

Original issue reported on code.google.com by [email protected] on 20 Oct 2013 at 10:20