Unsafe write encoded string 3

Another attempt at getting WriteEncodedString* across the line. This one is using the existing CharBuffer, and has removed the expanding component; so we shouldn't have any of the concerns that we have with the deserializer. I have included your original speed test (which does 'fail' sometimes, marginally), as well as the speed test with the list of objects. I have also made the code fully switchable with UseBufferedStringWriting flag.

Personally I think the buffer should be larger, but I'm trying to do the bare minimum to fit this in.

Existing master

	Serializing
	===========
	Single:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.0205          0.0205
	Answer  0.0861          0.0861
	Question        0.52535         0.5198

	Lists:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.1035          0.103
	Answer  0.3181          0.3194
	Question        1.7821          1.7672

	Dictionaries of strings to:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.6072          0.609
	Answer  2.10115         2.1344
	Question        7.7844          7.77235

Using the 36-byte buffer

	Serializing
	===========
	Single:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.0169          0.0165
	Answer  0.0548          0.0557
	Question        0.3632          0.36025

	Lists:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.0731          0.0731
	Answer  0.2146          0.2146
	Question        1.2257          1.22415

	Dictionaries of strings to:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.4252          0.4272
	Answer  1.49945         1.4903
	Question        5.755           5.6945

Doubleing the buffer to 72-byte-buffer

	Serializing
	===========
	Single:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.0133          0.0133
	Answer  0.0481          0.0481
	Question        0.3279          0.327

	Lists:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.0678          0.0682
	Answer  0.1949          0.1936
	Question        1.1039          1.10725

	Dictionaries of strings to:
	Type    Jil Static MS   Jil Static      Jil Dynamic MS  Jil Dynamic
	User    0.4007          0.3948
	Answer  1.3966          1.3944
	Question        5.5145          5.53215

Obviously this is a replacement for the other pull request if this one is accepted.