FieldProp(sequence): extend sequence ability for normal integer field

[wenchy]

tableau/proto/tableau/protobuf/tableau.proto

Lines 209 to 211 in 3a3f5cb

	// Ensure this field's value is a sequence and begins with this value.
	// Mainly used for map key and list element.
	optional int64 sequence = 4;

Example

In some situations, the developler want to compress the strorage size with bitset. So the bitset index column should be provided, and usually is a sequence started with 0.

ID	Index	Desc
Map<uint32, Chapter>	uint32|{sequence:0}	string
Chapter's ID	Chapter's Index	Chapter's desc
1001	0	desc1
1002	1	desc2
1003	2	desc3