Add G1GC & GC log config

[imbajin]

No description provided.

[codecov]

Codecov Report

Merging #616 into master will increase coverage by 0.42%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #616      +/-   ##
============================================
+ Coverage     71.94%   72.36%   +0.42%     
- Complexity     3640     3740     +100     
============================================
  Files           219      218       -1     
  Lines         16882    17296     +414     
  Branches       2399     2437      +38     
============================================
+ Hits          12145    12517     +372     
- Misses         3475     3498      +23     
- Partials       1262     1281      +19

Impacted Files	Coverage Δ	Complexity Δ
...m/baidu/hugegraph/backend/query/IdPrefixQuery.java	53.57% <0%> (-7.15%)	7% <0%> (-1%)
...java/com/baidu/hugegraph/schema/SchemaElement.java	80% <0%> (-5.72%)	18% <0%> (ø)
...aidu/hugegraph/backend/id/SplicingIdGenerator.java	90.9% <0%> (-4.33%)	11% <0%> (ø)
...aph/backend/store/postgresql/PostgresqlTables.java	87.34% <0%> (-4.04%)	1% <0%> (ø)
...java/com/baidu/hugegraph/type/define/DataType.java	87.32% <0%> (-2.54%)	36% <0%> (ø)
.../java/com/baidu/hugegraph/structure/HugeIndex.java	67.1% <0%> (-1.82%)	22% <0%> (+2%)
...gegraph/backend/serializer/BinaryBackendEntry.java	59.21% <0%> (-1.61%)	19% <0%> (+1%)
.../hugegraph/backend/store/rocksdb/RocksDBTable.java	78.26% <0%> (-1.09%)	32% <0%> (-1%)
...u/hugegraph/traversal/optimize/HugeVertexStep.java	68.91% <0%> (-0.82%)	17% <0%> (-1%)
.../hugegraph/backend/store/rocksdb/RocksDBStore.java	74.81% <0%> (-0.48%)	54% <0%> (ø)
... and 33 more

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[javeme]

add a option to switch whether to use g1

[javeme]

prefer -g g1

[javeme]

add default "" case