Improved Guid support

[ejball]

We should add a GuidFormat connector option that specifies how the Guid type is read/written.

Option	Description
Char36	All columns of CHAR(36) are read/written as Guid using lowercase hex and hyphens. (Current default behavior.)
Char32	All columns of CHAR(32) are read/written as Guid using lowercase hex without hyphens.
Binary16	All columns of BINARY(16) are read/written as Guid using big-endian byte order. Matches UUID_TO_BIN(x).
TimeSwapBinary16	All columns of BINARY(16) are read/written as Guid using big-endian byte order with time parts swapped. Matches UUID_TO_BIN(x,1).
OldBinary16	All columns of BINARY(16) are read/written as Guid using little-endian byte order. (Current behavior when OldGuids=True.)
None	Guid is not supported. CHAR(36) and CHAR(32) are read/written as strings; BINARY(16) is read/written as a byte array.

[ejball]

Work in progress: master...ejball:guids

[bgrainger]

Added in 0.41.0.