[Java][jersey1] add Java6 support to Java (jersey1) API client (#3919)

* add java6 support to java jersey1

* properly handle boolean value in mustache tag

* add test for supportJava6 option

modules/swagger-codegen/src/main/resources/Java/pojo.mustache

@@ -79,6 +79,7 @@ public class {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{{#parcela
 
   {{/vars}}
 
+{{^supportJava6}}
   @Override
   public boolean equals(java.lang.Object o) {
     if (this == o) {
@@ -99,6 +100,7 @@ public class {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{{#parcela
     return Objects.hash({{#vars}}{{name}}{{#hasMore}}, {{/hasMore}}{{/vars}}{{#parent}}{{#hasVars}}, {{/hasVars}}super.hashCode(){{/parent}});
   }
 
+{{/supportJava6}}
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder();