Compatible with more date formats

[javeme]

Expected behavior 期望表现

The following formats are accepted for date type:
yyyy-MM-dd
yyyy-MM-dd HH:mm:ss
yyyy-MM-dd HH:mm:ss.SSS

Actual behavior 实际表现

{
"message": "Unparseable date: "2016-1-1", expect format: yyyy-MM-dd HH:mm:ss.SSS",
"Exception-Class": "java.lang.IllegalArgumentException",
"exceptions":[
"java.lang.IllegalArgumentException"
],
"stackTrace": "java.lang.IllegalArgumentException: Unparseable date: "2016-1-1", expect format: yyyy-MM-dd HH:mm:ss.SSS\n\tat com.google.common.base.Preconditions.checkArgument(Preconditions.java:146)\n\tat com.baidu.hugegraph.util.E.checkArgument(E.java:56)\n\tat com.baidu.hugegraph.type.define.DataType.valueToDate(DataType.java:138)\n\tat com.baidu.hugegraph.schema.PropertyKey.convSingleValue(PropertyKey.java:185)\n\tat com.baidu.hugegraph.schema.PropertyKey.convValue(PropertyKey.java:152)\n\tat com.baidu.hugegraph.traversal.optimize.TraversalUtil.validPredicateValue(TraversalUtil.java:562)\n\tat com.baidu.hugegraph.traversal.optimize.TraversalUtil.convPredicateValue(TraversalUtil.java:487)\n\tat com.baidu.hugegraph.traversal.optimize.TraversalUtil.convHasStep(TraversalUtil.java:473)\n\tat com.baidu.hugegraph.traversal.optimize.TraversalUtil.convAllHasSteps(TraversalUtil.java:466)\n\tat com.baidu.hugegraph.traversal.optimize.HugeVertexStepStrategy.apply(HugeVertexStepStrategy.java:49)\n\tat org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversalStrategies.applyStrategies(DefaultTraversalStrategies.java:86)\n\tat org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.applyStrategies(DefaultTraversal.java:119)\n\tat org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.hasNext(DefaultTraversal.java:191)\n\tat org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils.fill(IteratorUtils.java:62)\n\tat org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils.list(IteratorUtils.java:85)\n\tat org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils.asList(IteratorUtils.java:382)\n\tat org.apache.tinkerpop.gremlin.server.handler.HttpGremlinEndpointHandler.lambda$channelRead$1(HttpGremlinEndpointHandler.java:239)\n\tat org.apache.tinkerpop.gremlin.util.function.FunctionUtils.lambda$wrapFunction$0(FunctionUtils.java:36)\n\tat org.apache.tinkerpop.gremlin.groovy.engine.GremlinExecutor.lambda$eval$2(GremlinExecutor.java:320)\n\tat java.util.concurrent.FutureTask.run(FutureTask.java:266)\n\tat com.baidu.hugegraph.auth.HugeGraphAuthProxy$ContextTask.run(HugeGraphAuthProxy.java:282)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)\n\tat java.lang.Thread.run(Thread.java:745)\n"
}