Fix vertex number id serailized in string

[Linary]

fix hugegraph/hugegraph-client#90

Change-Id: I272a6f9aa7395aabf3f8cdc280ebd4fd5afa575e

[codecov]

Codecov Report

Merging #1109 into master will increase coverage by 8.85%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #1109      +/-   ##
============================================
+ Coverage     60.35%   69.21%   +8.85%     
- Complexity     4709     5599     +890     
============================================
  Files           331      331              
  Lines         26997    27117     +120     
  Branches       3865     3896      +31     
============================================
+ Hits          16295    18769    +2474     
+ Misses         8915     6492    -2423     
- Partials       1787     1856      +69     

Impacted Files	Coverage Δ	Complexity Δ
...in/java/com/baidu/hugegraph/api/graph/EdgeAPI.java	54.68% <0.00%> (ø)	0.00 <0.00> (ø)
.../java/com/baidu/hugegraph/api/graph/VertexAPI.java	36.80% <0.00%> (ø)	0.00 <0.00> (ø)
...com/baidu/hugegraph/serializer/JsonSerializer.java	45.34% <0.00%> (-0.54%)	0.00 <0.00> (ø)
...ava/com/baidu/hugegraph/serializer/Serializer.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ackend/store/cassandra/CassandraStoreProvider.java	50.00% <0.00%> (-50.00%)	3.00% <0.00%> (-3.00%)
...om/baidu/hugegraph/backend/query/QueryResults.java	71.15% <0.00%> (-10.48%)	40.00% <0.00%> (+1.00%)	⬇️
...aph/backend/store/cassandra/CassandraFeatures.java	70.00% <0.00%> (-10.00%)	14.00% <0.00%> (-2.00%)
...com/datastax/driver/core/querybuilder/Clauses.java	73.91% <0.00%> (-8.70%)	2.00% <0.00%> (-2.00%)
...h/backend/store/cassandra/CassandraSerializer.java	85.71% <0.00%> (-4.77%)	26.00% <0.00%> (-1.00%)
...egraph/backend/store/cassandra/CassandraTable.java	75.88% <0.00%> (-4.26%)	80.00% <0.00%> (-4.00%)
... and 142 more

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