Serialization optimization for API layer

[Linary]

Tinkerpop serialize(ms)	JsonUtil serialize(ms)
50.90431	34.76242
17.685196	2.64178
6.967978	0.613692
6.376805	0.557116
7.061885	0.580705
5.450529	1.034863
6.243331	0.528445
3.592669	0.56928
6.72455	1.04227
3.659169	0.766351
3.869669	0.577642
3.697116	0.725209
4.275841	0.505675
3.957558	0.497075
3.297867	0.704811
3.476497	1.321159
5.778405	0.582425
3.184258	0.640752
3.355601	0.505587
4.073625	0.470232
3.975989	0.446233
5.556072	0.500786
4.225401	0.732474
2.80737	0.483586
2.726609	0.525542
3.545936	0.454052
3.940741	0.456917
4.493989	0.445915
4.007579	0.607158
3.582214	0.441222
3.308724	1.629057
4.189565	0.467643
3.465184	0.641506
3.318984	0.471381
2.917337	0.461303
3.431023	0.419186

[Linary]

#332